TYPO3 Core

For version 9, we want to rework the admin panel with the following goals:

• Easier to extend for extension authors (currently no new tabs are possible, the JS "API" is weird...)
• Modern Design
• More functionality (for inspiration see features of https://github.com/Konafets/typo3_debugbar and https://extensions.typo3.org/extension/typo3profiler/ )

• Extract `AdminPanelView` modules to one class per module with interface and API to register own modules (#84045)
• Extract module specific code lines from general code (interface expansion might be necessary) (#84118)
• Move AdminPanel to own system extension (#84159) and let the modules be registered by the corresponding core extensions (f.e. fe_edit)
• Remove access to globals and use PSR-7 request object instead (introduce AdminPanel PSR-15 middleware) [interface expansion with $request might be necessary]
• Add upgrade wizard to optionally enable admin panel on upgrades (#84583)
• Remove configuration via $_GET params (google the admin panel get vars and you'll see one of the reasons) (#84584)
• Render modules via fluid standalone (done)
• Render outer panel via fluid standalone (#84584)
• Re-Design the panel (#84584)
• Add functionality (tbd)