[!!!][FEATURE] Automatically register toolbar items as container services

Toolbar items are now automatically tagged and registered, based on
the implemented `ToolbarItemInterface`, using the autoconfiguration
feature from the DI container.

The registration via `$GLOBALS['TYPO3_CONF_VARS']['BE']['toolbarItems']`
has been removed.

Resolves: #96041
Related: #62928
Releases: master
Change-Id: Ic3d84752f30444d5a6be67ecbfe39e525c68e9ac
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72241


Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>