[TASK] Remove deprecated code from Core

Furthermore there is outstanding code to be
removed which is deprecated.

Resolves: #26508
Releases: 6.1
Change-Id: Ic2fa23d9d87fa81c6ec4526afba2d75064a693bc
Reviewed-on: https://review.typo3.org/1799
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter
Reviewed-by: Wouter Wolters
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack