[FEATURE] Introduce events to modify CKEditor configuration

This patch introduces a set of PSR-14 Events to modify
the CKEditor configuration.

- AfterGetExternalPluginsEvent
- BeforeGetExternalPluginsEvent
- AfterPrepareConfigurationForEditorEvent
- BeforePrepareConfigurationForEditorEvent

Resolves: #88818
Releases: master
Change-Id: I1f810e31274a05d52082de5e03fc530b3cee1a44
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/59304


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>