K8SPS-456: Allow setting custom environment variables

[0xAX]

This commit adds support for defining .Values.mysql.env which will be propagated to the PerconaServerMySQL and as a result to the MySQL statefulset. That could be useful especially since Percona MySQL operator added support for BOOTSTRAP_READ_TIMEOUT.

[it-percona-cla]

All committers have signed the CLA.

[0xAX]

@jvpasinatto hello, is there any chances it can be reviewed?

[valmiranogueira]

Hi @0xAX, this is already included in the scope for release 1.0.0, that is scheduled for today. Thank you for wanting to contribute nonetheless. Your initiative is truly appreciated.

[0xAX]

@valmiranogueira Thank you!