[TASK] Deprecate various public TSFE properties

Various properties can be accessed directly via
TypoScript config settings.

* $TSFE->spamProtectEmailAddresses
* $TSFE->intTarget
* $TSFE->extTarget
* $TSFE->fileTarget
* $TSFE->baseUrl

They have been marked as deprecated.

In addition, some internal functionality is now
marked as @internal as well, somehow related to
the deprecated properties.

Resolves: #97866
Releases: main
Change-Id: Ieecd1674783a1d9b9092528d16a988568e857e18
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75040


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>