Fixes #112200

Fixes #100853

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

* wip 2

* use viewlet stubs

* fix layering issue

* fix saveState and contextmenus

* move context menu logic into panecomposite

* revert tasks.json

* tasks again

* add showHeaderInTitleWhenSingleView values

* patch tests

* some cleanup

* more cleanup

* start view

* merging conflicts

* fix title and dnd

* adding missing api surface to pane composite

* additional merge resolution

Fixes https://github.com/microsoft/vscode-remote-release/issues/1902

Fixes https://github.com/microsoft/vscode/issues/86039

* rename splitview panels to panes

* rename files

* customViewPane

Part of https://github.com/microsoft/vscode-remote-release/issues/1847

Part of https://github.com/microsoft/vscode-remote-release/issues/1847

Part of https://github.com/microsoft/vscode-remote-release/issues/1778

For #81574

Fix microsoft/vscode-remote-release#1426

* strict init

* more strict props

* More strongly typed events

* Fixed typo

Using `object` causes errors if we disable `suppressImplicitAnyIndexErrors`

Part of #74250

- Extend `Disposable` in classes where it makes sense
- Use `DisposableStore` for lists of disposables
- Make `combinedDisposable` take arguments instead of an array (so that you can't pass in an array and then modify the array after the fact)