[stable/polaris]: allow to define additional podAnnotations

[sando38]

Why This PR? Allow to define custom annotations on the pod level.

Using the pod level annotations, I can for example specify istio sidecar memory and CPU limits.

Changes Changes proposed in this pull request:

• Allow to define pod level annotations

Checklist:

• [x] I have included the name of the chart in the title of this PR in square brackets i.e. [stable/goldilocks].
• [ ] I have updated the chart version in Chart.yaml following Semantic Versioning.
• [x] Any new values are backwards compatible and/or have sensible default.
• [x] Any new values have been added to the README for the Chart, or helm-docs --sort-values-order=file has been run for the charts that support it.

[CLAassistant]

All committers have signed the CLA.