Helm Pinot chart: add optional namespace, workload annotations, and minion image override

### Summary
I opened a PR to upstream a small set of backward-compatible Helm chart improvements from our production usage.

### Related PR

[https://github.com/apache/pinot/pull/18793](https://github.com/apache/pinot/pull/18793)

### What this issue tracks
This issue tracks review and merge of the following chart improvements:

* Optional namespace creation via a values flag
* Workload-level annotations for controller, broker, server, minion, and stateless minion workloads
* Optional minion-specific image override with fallback to the main image values
* Minor template whitespace cleanup in server configmap rendering

### Why this is needed
These changes improve operational flexibility (namespace management, annotations for platform integrations, independent minion image control) while preserving current behavior by default.

### Backward compatibility
All new knobs default to no-op behavior:

Namespace creation remains disabled unless explicitly enabled
Annotation maps default to empty
Minion image override falls back to existing image settings when not set

Thanks guys!

Start by reading the linked pull request, which contains the chart changes tracked here, and review its handling of namespace creation, workload annotations, minion image fallback, and server ConfigMap whitespace. Done means the PR is reviewed and merged with the documented defaults and backward-compatible behavior preserved.

Written by the indexing model from the issue text.