[TASK] Move public TemplateService properties to protected

The properties are meant to be used only inside the class (and the
extended classes) itself.

Resolves: #83273
Releases: master
Change-Id: I550012bc377c6bb577747490fac3100d378a6fd6
Reviewed-on: https://review.typo3.org/52901


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>