docs(thanos): unhide configuration docs for thanos storage clients (backport k239)

[loki-gh-app]

Backport 1cd95f5 from #16051

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What this PR does / why we need it:

Unhides docs for configuring thanos storage clients. This will be made available in the next minor release.

Special notes for your reviewer:
I made a minor change to the docs generator to not expand inline root blocks to avoid repetition. We can make this configurable by a doc tag doc:"noexpand" if we want to control this behavior

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

[github-actions]

💻 Deploy preview deleted.

[ashwanthgoli]

lgtm