K8SPG-254: Major upgrade support

CHANGE DESCRIPTION

We add a new CRD called `PerconaPGUpgrade` and a controller to reconcile major upgrades.

In the upstream, user needs to do the following manually to start major upgrades:
1. Pause cluster
2. Annotate cluster with upgrade object name
3. Resume cluster after upgrade is finished

Our controller automates these steps for user.

**Custom extensions**

If user has custom extensions installed in their cluster, we need to
consider them during upgrades. For this user needs to build and package
their custom extension for the major version they want to upgrade.
During upgrade we'll install extensions in the upgrade container using
the same mechanism, by injecting init containers.

**Caveats**

1. `pg_upgrade` duplicates the data in the same PVC for each major
   upgrade. Data for old version is not deleted automatically. That
   means user needs to be sure that their PVC have enough free space to
   store data.
2. If something went wrong with upgrade, cluster will remain paused.
   User needs to delete `PerconaPGUpgrade` object and  resume cluster
   themself to check what went wrong with upgrade.

CHECKLIST

Jira

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

Tests

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

Config/Logging/Testability

[x] Are all needed new/changed options added to default YAML files?
[x] Are the manifests (crd/bundle) regenerated if needed?
[x] Did we add proper logging messages for operator actions?
[x] Did we ensure compatibility with the previous version or cluster upgrade process?
[x] Does the change support oldest and newest supported PG version?
[x] Does the change support oldest and newest supported Kubernetes version?

Test name	Status
custom-extensions	passed
demand-backup	passed
init-deploy	passed
major-upgrade	passed
monitoring	passed
one-pod	passed
operator-self-healing	passed
pitr	passed
scaling	passed
scheduled-backup	passed
self-healing	passed
start-from-backup	passed
tablespaces	passed
telemetry-transfer	passed
upgrade-consistency	passed
upgrade-minor	passed
users	passed
We run 17 out of 17

percona / percona-postgresql-operator

K8SPG-254: Major upgrade support #789

CHANGE DESCRIPTION

CHECKLIST