Use ResizeObserver for monaco editor automaticLayout

- add count badge in extension viewlet
- show extensions in details page

This reverts commit 2f82bdcf.

Inherit theme text colour in Settings Editor's section headings

Fix #93292

- run additional file search over original query if limit hit and multiple inputs
- preserve existing highlights of symbols
- reduce flicker when having fast and slow results

Revert "Use the standard github token in places where we don't need to recursively trigger automations."

This reverts commit 6f2f1d6e.

Add two extra checks:
- Don't prompt users if the file extension doesn't change
- Don't prompt if only optional editors are available

Fix #91601

Allow extensions to contribute to terminal environments