K8SPG-730: add .status.observedGeneration for PerconaPGCluster

[pooknull]

https://perconadev.atlassian.net/browse/K8SPG-730

DESCRIPTION

This PR adds .status.observedGeneration for PerconaPGCluster resource

CHECKLIST

Jira

• Is the Jira ticket created and referenced properly?
• Does the Jira ticket have the proper statuses for documentation (Needs Doc) and QA (Needs QA)?
• Does the Jira ticket link to the proper milestone (Fix Version field)?

Tests

• Is an E2E test/test case added for the new feature/change?
• Are unit tests added where appropriate?

Config/Logging/Testability

• Are all needed new/changed options added to default YAML files?
• Are all needed new/changed options added to the Helm Chart?
• Did we add proper logging messages for operator actions?
• Did we ensure compatibility with the previous version or cluster upgrade process?
• Does the change support oldest and newest supported PG version?
• Does the change support oldest and newest supported Kubernetes version?

[JNKPercona]

Test Name	Result	Time
backup-enable-disable	passed	00:06:51
custom-extensions	passed	00:08:41
custom-tls	passed	00:04:52
demand-backup	passed	00:23:49
finalizers	passed	00:03:43
init-deploy	passed	00:03:13
monitoring	passed	00:07:19
monitoring-pmm3	passed	00:08:12
one-pod	passed	00:05:47
operator-self-healing	passed	00:08:00
pitr	passed	00:11:37
scaling	passed	00:04:45
scheduled-backup	passed	00:29:00
self-healing	passed	00:09:05
sidecars	passed	00:02:32
start-from-backup	passed	00:10:48
tablespaces	passed	00:07:43
telemetry-transfer	passed	00:03:23
upgrade-consistency	passed	00:05:13
upgrade-minor	passed	00:05:45
users	passed	00:03:30
We run 21 out of 21		02:53:56

commit: 972e045
image: perconalab/percona-postgresql-operator:PR-1199-972e04538