Fix memory leak in DockPanelRenderer and ToolbarAwareTabBar

[Hanksha]

What it does

This PR fixes a memory leak occurring in the DockPanelRenderer and ToolbarAwareTabBar when the user opened and closed a lot of tabs repeatedly. The DockPanelRenderer was not disposing the core preferences listener when the ToolbarAwareTabBar is disposed and the ToolbarAwareTabBar itself didn't dispose the TabBarToolbar when it is detached.

Fixes #13323

How to test

I've added a playwright test to test this issue in "/examples/playwright/src/tests/theia-application-shell.test.ts". Just remove the skip and run the test then check the logs for memory leak warnings.

Review checklist

• [x] As an author, I have thoroughly tested my changes and carefully followed the review guidelines

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