This reverts commit 38fbba35.

Switches builtin extensions to use @types/node for node definitions. Fixes a few errors that show up as a result of updating to a more modern version of node.d.ts

* Remove unneeded d.ts files from extensions

Moves most extensions to use the lib files for the standard library that typescript provides.

* Remove a few more node.d.ts references

- 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.