fix(helm): Fix GEL image tag, bucket name and proxy URLs

[monodot]

What this PR does / why we need it:
The chart doesn't currently seem to deploy GEL without having to do a couple of workarounds. This PR:

• Updates the image tag referenced in the deployment to the correct 3.0.1 (without the v prefix).
• Respects the user's admin bucket name.
• Adds the correct downstream proxy URLs in the enterprise-gateway for deployments in SSD mode (the Ring Health tab in the Grafana Enterprise Logs plugin was otherwise unable to list the nodes in SSD).

Which issue(s) this PR fixes:
Fixes #12845

Special notes for your reviewer:

• I have updated the image tag manually here to get the chart working, but I think the grafanabot job will also need to be updated (the one that gets the latest tag and inserts it into the Helm chart), otherwise this change will be overwritten on the next release. For that, there's an Issue here: https://github.com/grafana/enterprise-logs/issues/2381
• I have reverted to using the user's configured bucket name for the admin bucket, could you please confirm it looks correct?

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
• 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.

[trevorwhitney]

Looks great, thanks for catching these. Can you add a default for the admin bucket only in the case of using minio, and make sure it's empty otherwise?

[trevorwhitney]

good catch, looks like we broken this in #12548. Would you mind adding a default for this value only in the case where both minio and enterprise are enabled? Otherwise there should be no default so we don't run into the problem fixed in #12548

[monodot]

I've updated this now. I've separated the admin storage config out into its own separate Helm value (enterprise.adminClientConfig), which includes a default for Minio only.

To set any other storage options (e.g. AWS, GCS, etc), users can just override that adminClientConfig value.

[trevorwhitney]

Ideally a user only has to provide loki.storage.bucketNames and everything else should just work. I think we should default the admin config to use loki.storage.bucketNames.admin in all cases but minio, and in the minio case we can hardcode it. I don't think we want to force a user to have to provide a whole adminClient section when they are not using minio.

[trevorwhitney]

looks great, thanks for addressing all my feedback!