feat(config): set rule version record limit by default, bump grafana to 11.3.0

[weisdd]

Changes

• set rule_version_record_limit to 5 by default:
  • Prior to Grafana 11.3.0, alert_rule_version table would uncontrollably grow to accommodate multiple copies of alert rules;
  • In Grafana 11.3.0, a new field (rule_version_record_limit, which is part of unified_alerting section) was introduced to enforce a limit on the rule versions. It is set to 0 there by default. To mitigate the behaviour, this PR instructs the operator to set the value to 5 by default;
• Other changes:
  • bumped the default Grafana version to 11.3.0 (I can drop that commit if needed).

Backwards compatibility

If someone wants to preserve the previous behaviour or postpone initial database cleanup, it's possible to pass:

apiVersion: grafana.integreatly.org/v1beta1
kind: Grafana
# omitted
spec:
  config:
    # omitted
    unified_alerting:
      rule_version_record_limit: "0"

Fixes: #1639