Implement source.fixAll.regal code action

[anderseknert]

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_codeAction

        /**
	 * Base kind for a 'fix all' source action: `source.fixAll`.
	 *
	 * 'Fix all' actions automatically fix errors that have a clear fix that
	 * do not require user input. They should not suppress errors or perform
	 * unsafe fixes such as generating new types or classes.
	 *
	 * @since 3.17.0
	 */

I imagine this would simply invoke regal fix in the given file. One nice thing about this is that editors like VS Code provide options for running all the source.fixAll actions on save.

Some good context here.