[Backport 1.x] Allow user-defined labels on pvcs

[simonstumpf]

Description

[Backport 1.x] Add support for user-defined labels on PVCs.

Issues Resolved

Closes #554
Backport #591

Check List

• Commits are signed per the DCO using --signoff

For any changes to files within Helm chart directories:

• Helm chart version bumped
• Helm chart CHANGELOG.md updated to reflect change

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[prudhvigodithi]

Thanks @simonstumpf, backport of #591.
Adding @peterzhuamazon

[prudhvigodithi]

@simonstumpf can you please fix the failing CI's?
Thanks

[peterzhuamazon]

Not sure why is the failure tho, pinging @simonstumpf

Installing chart with values file 'charts/opensearch/ci/ci-rbac-enabled-values.yaml'...

Creating namespace 'opensearch-wh6i31dni7'...
>>> kubectl create namespace opensearch-wh6i31dni7
namespace/opensearch-wh6i31dni7 created
>>> helm install opensearch-wh6i31dni7 charts/opensearch --namespace opensearch-wh6i31dni7 --wait --values charts/opensearch/ci/ci-rbac-enabled-values.yaml --timeout 1000s
Error: The operation was canceled.

Thanks.

[peterzhuamazon]

I am fixing this and merging.