[BUGFIX] Deprecated function call mysql_list_dbs in dbal

replaced mysql_list_dbs by show databases query

Resolves: #53761
Releases: 6.2
Change-Id: I2b41b19aa900ba7eef33f2a990c8c029cbc1c08c
Reviewed-on: https://review.typo3.org/26390
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Oliver Klee
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind