feat(kafka): update existing topic partitions and configs during provisioning

[bhataprameya]

What

Extends the external Kafka provisioning Job to update existing topics, not just
create them. After the initial --create --if-not-exists pass, a second pass now:

• Increases partition counts when the desired value in values.yaml exceeds the
  live topic's current partition count.
• Applies topic-level config changes (e.g. retention.ms, cleanup.policy,
  min.compaction.lag.ms) when the live config differs from the desired state.

Why

Previously, the provisioning Job was create-only — if a topic already existed, any
configuration drift (partition count, cleanup policy, compaction lag, etc.) was
silently ignored. Operators had to manually alter topics via Kafka CLI. This change
makes the Job idempotent and convergent: it drives topics toward the desired state
on every helm upgrade.

Details

• Partition increases use kafka-topics.sh --alter --partitions.
• Detection is done by comparing --describe output against desired values; updates
  are skipped when already in sync.