Many `Promise.resolve(null)` should actually be `Promise.resolve(void 0)`. In other cases, we were missing a null return annotation.

Fixes a common type error

Fixes #65031

Adds a `enableForWorkspaceTypeScriptVersions` flag (default false) to the plugins contributions that  allows a contributed plugin to be loaded for workspace versions of ts

And better management of these actions.

Fix #59635

Fixed #58159 by triggering a layout refresh to work around xtermjs bug…

Fixes #64390

Part of #64390

Fixes #64865