Helm: add commonLabels (#9067)

[ftrigari]

What this PR does
Every object created by the chart could have custom labels.

Which issue(s) this PR fixes or relates to
Fixes #9067

--- EDIT ---

I made a mess with my branch. I erased all and created a new commit.
This is the old PR #9742

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[NickAnge]

Thanks @ftrigari for the change. Could you please update CHANGELOG, with the addition ? Thanks in advance

[ftrigari]

Hi @NickAnge,
I updated the changelog file.
Thank you

[narqo]

Could you add a unit-test for this change? I don't think it's worth having a separate test, so maybe only add a simple case to the existing test-oss-values.yaml.

After that, you'll need to run make build-helm-tests in the project's root to regenerate the assets for this test. With that it'll be easier to track future changes around the values, to make sure we don't break it.

[narqo]

I'm not sure what is the use-case for the feature, but I should point out that — in the current implementation — the global.commonLabels seem to only add labels to the top-level resources (e.g. deployments, statefulsets, configmaps, etc). It doesn't add labels to the resources, controlled by those top-levels, e.g. pods, that a deployment creates. This may be fine.