[TASK] Replace TCA cache with serialized array

The TCA isn't stored as php array anymore,
but instead as serialized array string. Unserialize
seems to be much faster in this regard although
opcode caches have been tested.

Resolves: #53747
Releases: 6.2
Change-Id: I540cae2ecee0ef09635ceff0b91b7a940dae01f7
Reviewed-on: https://review.typo3.org/25492
Reviewed-by: Alexander Opitz
Tested-by: Alexander Opitz
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Thomas Maroschik
Tested-by: Thomas Maroschik