vpa: Pod Monitors for prometheus metrics

[digiserg]

Why This PR?
I want to get the VPA metrics in proemtheus

Fixes #

Changes
Changes proposed in this pull request:

• adds optional podMonitor configuration

Checklist:

• 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.
• Any new values are backwards compatible and/or have sensible default.
• 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.

[sudermanjr]

Hello, thanks for the PR!

I recommended a different version change due to the fact that we are adding functionality (according to semver that's a minor version change). Also, could you please add documentation strings to the new values that are being added?

[sudermanjr]

Docs strings. You'll need to run helm-docs --sort-values-order=file to have them update the readme.

[sudermanjr]

Seems like we need helm/chart-testing#531 to be merged so that we can start disabling that. We're definitely failing at the reuse-values step right now

[sudermanjr]

LGTM. Thanks!