fix(helm): inadvertent accumulation of podLabels using merge

[schahal]

What this PR does / why we need it:

See this issue:

the labels under .Values.write.podLabels suddenly appear in all deployments and statefulsets because they are inadvertently leaked into .Values.loki.podLabels. The root cause of this problem can be traced back to a change in #16062, which incorrectly utilizes the merge function. The merge function modifies the source object[...]

Which issue(s) this PR fixes:

Fixes #16616 and #16617

Special notes for your reviewer:

I got the deepCopy suggestion from helm/helm#13308 (comment)

I tested chart locally before and after change and saw my podLabels as they should be

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[balmeida-nokia]

Suggesting an alternative way to deal with merge. Regardless, both ways are valid

[balmeida-nokia]

@schahal I'm not from loki, so I can't approve or reject. I just thought I could be useful. So I can't do anything productive about the review request, sorry.

[schahal]

@poyzannur @bentonam @JStickler : I feel I followed Contributing.md and updated CHANGELOG just now as it'd suggested: is there anything else we should do to move this forward?

I tagged you as this should fix a bug that was introduced in #16062 and I'm stuck on the v1.26.0 release due to me needing specific labels on certain workloads (and prefer not to manage an out-of-band chart).

Thanks in advance!

[Jayclifford345]

Hey @schahal, thanks for this I shall get this pushed through internally for review :)

[poyzannur]

Sorry to miss the ping @schahal
I remember the original PR, ah we missed that too.
Please rebase and resolve conflicts, otherwise it LGTM i'll be approving after.

[schahal]

Thanks @poyzannur ! All up-to-date!