Extension Packs

Splits the markdown scroll sync settings to be more granular.

Fixes #19074

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

Move configuring language based settings to preferences and expose it as an API from preferences service

Fix for #16771. 

Support undo and redo in input fields (fixes #151)

Add Markdown Preview to Editor Scroll Syncronization

Reindent all lines

fixes #18853

Use named pipes to talk to extension host