refactor!: consolidate Lua registry sources and the Package API (#1498)

**This removes the following APIs:**
- `Package:check_new_version()`. Instead use the new `Package:get_latest_version()`.

**This has a breaking change in the following APIs:**
- `Package:get_installed_version()` now no longer takes a callback but instead returns the installed version or `nil` if
  not installed.

<details>
<summary>To handle these breaking changes in plugins, leverage the `mason.version` module, for example:</summary>

```lua
local mason_version = require("mason.version")
local registry = require("mason-registry")
local pkg = registry.get_package("rust-analyzer")

if mason_version.MAJOR_VERSION < 2 then
    -- before
    pkg:check_new_version(function (success, new_version)
        -- …
    end)
    pkg:get_installed_version(function (success, installed_version)
        -- …
    end)
else
    -- after
    local new_version = pkg:get_latest_version()
    local installed_version = pkg:get_installed_version()
fi
```

</details>

---

<details>
<summary>This change also introduces breaking changes for Lua registry sources, by consolidating the package schema with the
registry.</summary>

The following is an example of a package defined in a Lua registry, following the new schema:

```lua
local Pkg = require("mason-core.package")

return Pkg.new {
    schema = "registry+v1",
    name = "ripgrep",
    description = "ripgrep recursively searches directories for a regex pattern while respecting your gitignore.",
    homepage = "https://github.com/BurntSushi/ripgrep",
    licenses = { Pkg.License.MIT },
    languages = {},
    categories = {},
    source = {
        id = "pkg:mason/ripgrep@13.0.0",
        ---@param ctx InstallContext
        ---@param purl Purl
        install = function(ctx, purl)
            -- Arbitrary installation code.
        end,
    },
    bin = {
        rg = "./bin/rg",
    },
}
```

</details>

4 files changed, 49 insertions, 21 deletions

diff --git a/lua/mason-core/installer/context.lua b/lua/mason-core/installer/context.lua
index 21c9c26f..a991cd9f 100644
--- a/lua/mason-core/installer/context.lua
+++ b/lua/mason-core/installer/context.lua
@@ -202,7 +202,7 @@ function InstallContext.new(handle, opts)
     local cwd_manager = CwdManager.new(path.install_prefix())
     return setmetatable({
         cwd = cwd_manager,
-        spawn = ContextualSpawn.new(cwd_manager, handle, not handle.package:is_registry_spec()),
+        spawn = ContextualSpawn.new(cwd_manager, handle, false),
         handle = handle,
         package = handle.package, -- for convenience
         fs = ContextualFs.new(cwd_manager),
diff --git a/lua/mason-core/installer/init.lua b/lua/mason-core/installer/init.lua
index 994ab847..961c5c47 100644
--- a/lua/mason-core/installer/init.lua
+++ b/lua/mason-core/installer/init.lua
@@ -74,6 +74,7 @@ end
 ---@async
 ---@param context InstallContext
 function M.prepare_installer(context)
+    local installer = require "mason-core.installer.registry"
     return Result.try(function(try)
         local package_build_prefix = path.package_build_prefix(context.package.name)
         if fs.async.dir_exists(package_build_prefix) then
@@ -82,12 +83,7 @@ function M.prepare_installer(context)
         try(Result.pcall(fs.async.mkdirp, package_build_prefix))
         context.cwd:set(package_build_prefix)
 
-        if context.package:is_registry_spec() then
-            local registry_installer = require "mason-core.installer.registry"
-            return try(registry_installer.compile(context.handle.package.spec, context.opts))
-        else
-            return context.package.spec.install
-        end
+        return try(installer.compile(context.handle.package.spec, context.opts))
     end)
 end
 
diff --git a/lua/mason-core/installer/registry/init.lua b/lua/mason-core/installer/registry/init.lua
index e7c796e9..961e94ea 100644
--- a/lua/mason-core/installer/registry/init.lua
+++ b/lua/mason-core/installer/registry/init.lua
@@ -35,9 +35,10 @@ M.register_provider("nuget", _.lazy_require "mason-core.installer.registry.provi
 M.register_provider("opam", _.lazy_require "mason-core.installer.registry.providers.opam")
 M.register_provider("openvsx", _.lazy_require "mason-core.installer.registry.providers.openvsx")
 M.register_provider("pypi", _.lazy_require "mason-core.installer.registry.providers.pypi")
+M.register_provider("mason", _.lazy_require "mason-core.installer.registry.providers.mason")
 
 ---@param purl Purl
-local function get_provider(purl)
+function M.get_provider(purl)
     return Optional.of_nilable(PROVIDERS[purl.type]):ok_or(("Unknown purl type: %s"):format(purl.type))
 end
 
@@ -127,7 +128,7 @@ function M.parse(spec, opts)
         end
 
         ---@type InstallerProvider
-        local provider = try(get_provider(purl))
+        local provider = try(M.get_provider(purl))
         log.trace("Found provider for purl.", source.id)
         local parsed_source = try(provider.parse(source, purl, opts))
         log.trace("Parsed source for purl.", source.id, parsed_source)
@@ -213,16 +214,4 @@ function M.compile(spec, opts)
     end)
 end
 
----@async
----@param spec RegistryPackageSpec
-function M.get_versions(spec)
-    return Result.try(function(try)
-        ---@type Purl
-        local purl = try(Purl.parse(spec.source.id))
-        ---@type InstallerProvider
-        local provider = try(get_provider(purl))
-        return provider.get_versions(purl, spec.source)
-    end)
-end
-
 return M
diff --git a/lua/mason-core/installer/registry/providers/mason.lua b/lua/mason-core/installer/registry/providers/mason.lua
new file mode 100644
index 00000000..3490ebaa
--- /dev/null
+++ b/lua/mason-core/installer/registry/providers/mason.lua
@@ -0,0 +1,43 @@
+local Result = require "mason-core.result"
+local _ = require "mason-core.functional"
+
+local M = {}
+
+---@param source RegistryPackageSource
+---@param purl Purl
+function M.parse(source, purl)
+    if type(source.install) ~= "function" and type((getmetatable(source.install) or {}).__call) ~= "function" then
+        return Result.failure "source.install is not a function."
+    end
+
+    ---@class ParsedMasonSource : ParsedPackageSource
+    local parsed_source = {
+        purl = purl,
+        ---@type async fun(ctx: InstallContext, purl: Purl)
+        install = source.install,
+    }
+
+    return Result.success(parsed_source)
+end
+
+---@async
+---@param ctx InstallContext
+---@param source ParsedMasonSource
+function M.install(ctx, source)
+    ctx.spawn.strict_mode = true
+    return Result.pcall(source.install, ctx, source.purl)
+        :on_success(function()
+            ctx.spawn.strict_mode = false
+        end)
+        :on_failure(function()
+            ctx.spawn.strict_mode = false
+        end)
+end
+
+---@async
+---@param purl Purl
+function M.get_versions(purl)
+    return Result.failure "Unimplemented."
+end
+
+return M