[BUGFIX] Do not override template processors of fluid

Fluid defines it's own template processors that are currently overridden
in the TYPO3 Fluid rendering context.
This becomes important if fluid standalone adds template processors or adjusts
it's RenderingContext constructor like in
https://github.com/TYPO3/Fluid/pull/220

Change-Id: I69b044e308421665ea8c88be7789da1a4323828f
Resolves: #78651
Releases: master
Reviewed-on: https://review.typo3.org/50590


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>