refactor!: refactor installer internals and add new Package class methods (#1523)

This contains the following changes:
1) `Package:install()` now accepts a second, optional, callback argument which is called when installation finishes
   (successfully or not).
2) Adds a `Package:is_installing()` method.

This contains the following breaking changes:
1) `Package:install()` will now error when called while an installation is already ongoing. Use the new
   `Package:is_installing()` method to check whether an installation is already running.

This also refactors large portions of the tests by removing test globals, removing async_test, and adding the
`mason-test` Lua module instead. Test helpers via globals are problematic to work with due to not being detected through
tools like the Lua language server without additional configuration. This has been replaced with a Lua module
`mason-test`. `async_test` has also been removed in favour of explicitly making use of the `mason-core.async` API. These
changes stands for a significant portion of the diff.

1 files changed, 63 insertions, 0 deletions

diff --git a/lua/mason-core/installer/location.lua b/lua/mason-core/installer/location.lua
new file mode 100644
index 00000000..2cc038e4
--- /dev/null
+++ b/lua/mason-core/installer/location.lua
@@ -0,0 +1,63 @@
+local Path = require "mason-core.path"
+local Result = require "mason-core.result"
+local fs = require "mason-core.fs"
+
+---@class InstallLocation
+---@field private dir string
+local InstallLocation = {}
+InstallLocation.__index = InstallLocation
+
+---@param dir string
+function InstallLocation.new(dir)
+    return setmetatable({
+        dir = dir,
+    }, InstallLocation)
+end
+
+function InstallLocation:get_dir()
+    return self.dir
+end
+
+---@async
+function InstallLocation:initialize()
+    return Result.try(function(try)
+        for _, p in ipairs {
+            self.dir,
+            self:bin(),
+            self:share(),
+            self:package(),
+            self:staging(),
+        } do
+            if not fs.async.dir_exists(p) then
+                try(Result.pcall(fs.async.mkdirp, p))
+            end
+        end
+    end)
+end
+
+---@param path string?
+function InstallLocation:bin(path)
+    return Path.concat { self.dir, "bin", path }
+end
+
+---@param path string?
+function InstallLocation:share(path)
+    return Path.concat { self.dir, "share", path }
+end
+
+---@param path string?
+function InstallLocation:package(path)
+    return Path.concat { self.dir, "packages", path }
+end
+
+---@param path string?
+function InstallLocation:staging(path)
+    return Path.concat { self.dir, "staging", path }
+end
+
+---@param name string
+function InstallLocation:lockfile(name)
+    return self:staging(("%s.lock"):format(name))
+end
+
+return InstallLocation