Add a mechanism to be a customer of the extension host (share lifecycle) and begin reducing usage of IThreadService

TS 2.3.1 introduced a breaking change by [switching to covariant types for callbacks](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#covariance-in-callback-parameters). This change tries to fix these compiler errors in the workbench codebase

Fixes #24209

**Bug**
Currently, for the js/ts references code lens, even if there are zero references you can click on the lens. This display an empty peek view

**Fix**
Allow code lenses to only register a title for the lens with no actual backing command

introduces more changes to the SCM api

fixes #23623
fixes #23676

debt - no guessing-caching, better use of gc-signals, command converter using gc-signals, main side heap service

* a declared module allows to have a sibling module containing experimental API
* this change also cleans up some bogous type pollution that happened because vscode used to be both, a declare module and a global namespace