Enable debug image

When trying to recover from a crash or to debug other problems consider turning on the debug image.

Percona supplies the pxc-db image with the -debug suffix. This can be added by either adding it to your pxc-db-$ENVIRONMENT.yaml or (if you want it to not persist) by using kubectl edit statefulset pxc-db-pxc and changing the image tag accordingly to the version you are using.

pxc:
    ## before
    # tag: 8.0.20-11.1
    #
    ## after
    tag: 8.0.20-11.1-debug

After enabling the debug image, the pxc-db pods will log verbosely on stdout/stderr.