Add terminal editor icon and color support

Add extraClasses to editor input

Fixes #127000

Fixes #126689

Fixes #127074

Update debug theme styles

//cc @lramos15

* Revert "macOS - workaround fullscreen window regression (#125122)"
* Fixes https://github.com/microsoft/vscode/issues/125122
* Fixes https://github.com/microsoft/vscode/issues/126016
* Fixes https://github.com/microsoft/vscode/issues/126013
* Fixes https://github.com/microsoft/vscode/issues/122352
* Fixes https://github.com/microsoft/vscode/issues/126321

This enables consumers to style the tab without misappropriating the
file icon system

Part of #126689

See https://github.com/microsoft/vscode/issues/126987#issuecomment-867031454
This commit makes the following changes:

- Keep the `resolveChildrenHandler`, and remove the CancellationToken parameter
- Remove `TestITem.status` and instead have `TestItem.canResolveChildren?: boolean`
- Add `TestItem.busy?: boolean`. Note that the UI would implicitly show
  the item as busy while `resolve` is being called. (This is a new feature)

Upgrading to account for these changes should take around 10 to 20 minutes:

1. Where you previously set `item.status = vscode.TestItemStatus.Pending`,
   instead set `item.canResolveChildren = true`.
2. If you used the cancellation token in resolveChildrenHandler, you no
   longer need to do so. What you do here instead is up to you:

	 - If you set up global workspace watchers, add those to `context.subscriptions`
	 - You _probably_ don't need to set up watchers for "file" test items,
	   since you will receive updates via `vscode.workspace.onDidChangeTextDocument`
		 and/or any FileWatcher you have set up.

Example of an update: https://github.com/microsoft/vscode-selfhost-test-provider/commit/7287c64bf72f4ed037a3cb57f05220bbe1b38d84