Attach cluster config map labels at creation time

We attach a set of labels to config maps that we create to ease the manual cleanup by users in case Flink fails unrecoverably.

For cluster config maps (that are used for leader election), these labels are not set at creation time, but when leadership is acquired, in contrast to job config maps.

This means there's a gap where we create a CM without any labels being attached, and should Flink fail before leadership can be acquired it will continue to lack labels indefinitely.

AFAICT it should be straight-forward, at least API-wise, to set these labels at creation time.