feat(loki-helm): allow override namespace for loki helm chart

[lucasoares]

What this PR does / why we need it:

Allow overriding namespace for Loki helm chart resources.

Which issue(s) this PR fixes:
Fixes #8044

Special notes for your reviewer:

Waiting for feedback before updating changelogs/docs and chart version

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• CHANGELOG.md updated
  • If the change is worth mentioning in the release notes, add add-to-release-notes label
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• 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

[CLAassistant]

All committers have signed the CLA.

[bonddim]

Link issue from helm-charts grafana/helm-charts#3577

@grafana/loki-team

[Jayclifford345]

Hi @lucasoares, thank you for this, if you wouldn't fixing the conflicts I think this would be a nice edition to the helm