[BUGFIX] Have CKEditor link plugin keep tags

When using TYPO3's custom link plugin
for CKEditor, special tags / attributes
within the link (e.g. <em>) are now kept.

Previously, all custom tags were removed, as only
text was taken, but if the link was added without
the link plugin, the problem did not exist.

Resolves: #89404
Resolves: #93457
Releases: 11.5
Change-Id: I6f7152e927a4a4437dc0b3d3561ae6a7c56adedc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76404


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>