[BUGFIX] Better caching of TSconfig in BackendUtility for bulk inserts

Changes the cache of pageTSconfig from creating a cached entry for each
page to creating a cached entry for each different TSconfig (including
userTSconfig) and a hash-cache for each page instead.

Resolves: #63629
Releases: master, 6.2
Change-Id: I3e4c70cd46cec26dda8574c058d828ec2e22a385
Reviewed-on: http://review.typo3.org/35145
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>