[TASK] Improve Installer database selection step

Make the following adaption:
 * Change the order of the two options.
 * Preselect the first, empty, existing database.
 * Add a hint, that the user must have sufficient privileges
   to create a new database.

Resolves: #51931
Releases: 6.2
Change-Id: I823a194ddd1dc3aad2d560354bce20855c5c372c
Reviewed-on: https://review.typo3.org/23770
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters