chore: hide docs for thanos clients + restore original cli prefix

[ashwanthgoli]

What this PR does / why we need it:

Changes from this pr could result in a change of cli flags for projects relying on the thanos bucket pkg from Loki.

This changes restores a few things listed below:

• Revert the thanos storage config prefix to default value
• Register all providers cli flags, same as before
• Hide thanos storage config in loki docs since not all providers are supported yet

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

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