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>

1 files changed, 2 insertions, 6 deletions

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