- Revert changes to id in Ext description. No lowering of name.
- Implement an equal function to check equality of extensions
- Use above function to check the equality with extension description

- In Extension description in Extension host
- In Extension enablement service
- Rename identifier to id in IExtension

fixes #20983

fixes #20703

* Add Type Definition Provider API

Adds a new API to support type definition providers and adds an initial type definition provider for TypeScript

* Fix comment

* Addressing comments

* Fixer menu option ordering

* Added simple test

* Rename TypeDefinitionProvider to TypeImeplementationProvider

**bug**
In #18346, I originally called the new go to implementation provider api `ImplementationProvider` which we then decided to rename to `TypeDefinitionProvider`. At the time, I didn't realize that a type definition was actually its own, unrelated concept.

**Fix**
Rename `TypeDefinitionProvider` to `TypeImplementationProvider` to make it clear what the purpose and use of this api is.

* Fix a few names in comments

This may turn into an enum or change behavior soon pending on the result of
task-terminal integration. Removing from the API until more thought has been
put into it.

Part of #15583
Part of #18661

Adds an initial implementation of scroll synrconization from the markdown preview to the editor. When the preview is scrolled, automatically scrolls the editor to reveal the same location.

This required adding a new supported reveal type `AtTop` in our API. This is already supported and used internally, but not really exposed in the public apis (except for the `revealLine` command).

allow users to toggle between git and preview SCM