Properly implement MySQLi for DBAL native mode.

Resolves: #50752
Releases: 6.2
Change-Id: I0c36e7d2828c94cc7c726757f3adc086ffd68015
Reviewed-on: https://review.typo3.org/27875
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers
Reviewed-by: Anja Leichsenring
Reviewed-by: Markus Klein
Tested-by: Markus Klein