Add support for multiple rulers with different colors

Fixes https://github.com/microsoft/vscode/issues/89273

Fixes https://github.com/microsoft/vscode-remote-release/issues/2218

- register viewlets and panels for containers
- events when view visibility has changed
- small refactorings

Developed setting which controls whether the definition link opens element in the peek widget.

This reverts commit 5f58ff53, reversing
changes made to 6346697d.

Added contrib extension to have focus follow mouse (fixes #25685).

Fix 89899 - improve description of editor.foldingStrategy setting

Fix #89900 - improve text on editor.showFoldingControls setting

Style diff editor's scrollable viewport just like any other scrollbar

fixes microsoft/vscode-remote-release#2115