Alr.Platforms.Windows: use Alire.config in msys2 install (#443)

Alr.Platforms.Windows: use Alire.config in msys2 install (#443)

* Alr.Platforms.Windows: use Alire.config in msys2 install

* Update msys2 install script URL

Now that the master version is updated with install dir feature.

* Alire.Config.Edit: create directory for the config file in case it doesn't exists

* Alire.Config.Edit: improve TOML value evaluation

If first the value cannot be parsed, we directly create a TOML_String value instead of trying to parse it again between quotes.

* Alr.Platforms.Windows: remove unecessary call to YAML_Stringify