Fixes #12434

* Use the extension descriptions available in the UI thread
* Don't wait for handling extension points until extension host is running
* Create the extension host process only after extension points have been handled
* Send the initial configuration as part of the initData to the extension host

Load configuration for languages when they are first encountered as an embedded mode in TextMate (#14136)

This reverts commit b949f4f8.

Fixes #12434

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

fixes #12879

This reverts commit 2d1c94ab.