Update zpdb default regex

[tcp13equals2]

What this PR does

This PR updates the default regex used by the zone aware pod disruption budget.

The regex has been updated to support an optional -partition element in the pod name.

eg ingester-zone-a-partition-10 is now supported.

Note that this regex format is confirmed supported and tested in grafana/rollout-operator#349

Which issue(s) this PR fixes or relates to

This alternate pod name format is used within ingest storage upgrade/migration paths. Adding support for this ensures that the rollout-operator continues to function correctly during such migrations.

Checklist

• Tests updated.
• Documentation added.
• [ x] CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]. If changelog entry is not needed, please add the changelog-not-needed label to the PR.
• about-versioning.md updated with experimental features.

---

Note

Extends ZoneAwarePodDisruptionBudget pod name regex to accept optional -partition segment and updates regex group index, with corresponding changes in defaults and generated tests, plus changelog entry.

• Rollout Operator / Config:
  • Update default multi_zone_ingester_zpdb_partition_regex to '[a-z\-]+-zone-[a-z]-(partition\-)?([0-9]+)' and multi_zone_ingester_zpdb_partition_group to 2 in operations/mimir/multi-zone-ingester.libsonnet.
• Generated Tests:
  • Adjust ZoneAwarePodDisruptionBudget specs across generated YAMLs to use new podNamePartitionRegex and podNameRegexGroup (2) for ingester rollouts.
• Changelog:
  • Add enhancement entry noting regex now supports optional -partition in pod names.

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