* 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).

- Basing snippet insertion failure on a new `_codeEditor` null-check.
- Now returns `Thenable<boolean>`.
- Removed vscode.proposed.d.ts copy of the `TextEditor` change.
- Removing empty options interface.

TextEditor.edit snippet overload now returns void. No longer preventing when already in snippet mode.

doc - mention that status bar messages must be disposed, move signature down to encourage auto-dispose cases

* Add Go To Implementation Api

For #10806

Adds a new API for supporting  `go to implementation` command for languages. Implements an example for TS

* Rename

* Cleanup

Fixes #15583

More robust type validation on ext side of insertSnippet.
Position/range check for snippet insertion was inverted.
Adding insertSnippet to vscode.d.ts. (Should it be in vscode.proposed.d.ts?)
Adding extension API tests for insertSnippet.

* Add CompletionItemKind.Folder

Fixes #17435

Adds a new completion item kind for folder/directories. This is useful for path intellisense

For the icons, I copied the icons for folders into the suggestion icon set. Let me know if new ones are needed instead.

* Fix monaco.d.ts

Fixes #17356

 In description for ExtensionContext -> storagePath, links to globalState and workspaceState are incorrect and lead to an error page.

This reverts commit 492fda67.