Allow to temporarily stop LSP servers (#28034)

Same as `editor::RestartLanguageServer`, now there's an
`editor::StopLanguageServer` action that stops all language servers,
related to the currently opened editor.

Opening another singleton editor with the same language or changing
selections in a multi buffer will bring the servers back up.

Release Notes:

- Added a way to temporarily stop LSP servers

---------

Co-authored-by: Michael Sloan <mgsloan@gmail.com>

crates/editor/src/actions.rs

@@ -412,6 +412,7 @@ actions!(
         SortLinesCaseInsensitive,
         SortLinesCaseSensitive,
         SplitSelectionIntoLines,
+        StopLanguageServer,
         SwitchSourceHeader,
         Tab,
         Backtab,