[TASK] Use SimpleFileBackend for t3lib_l10n cache

The language cache by default uses the FileBackend to store its data.
Language cache entries need to be deleted only if new extensions are
loaded and if new language overlays are fetched. They do not need
tagging and can have an unlimited lifetime.
Switching to SimpleFileBackend removes the tagging and sets unlimited
lifetime by to reduce read and write load on this cache.

Change-Id: I5c4778f4c38ae369b6873574e961fa65208d77a1
Resolves: #52295
Related: #52125
Releases: 6.2, 6.1, 6.0
Reviewed-on: https://review.typo3.org/24080
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn