mysql8 db images: Test `mysqladmin ping` when waiting for mysqld startup

Merged and new docker images are rolled for dev

Tested dev image and ran pipeline several times, have not reproduced original issue, startup script seems to wait for DB to be ready before creating users. Opened merge request to prod images.

Delivered to production, maybe restart can use separate issue

Also it needs to explore ability to copy prepackaged DB instead of starting and creating users

let's fix encoding issue in #3468905: Update default system encoding setting for Mysql images →

Automatically closed - issue fixed for 2 weeks with no activity.