feat: add loki health command

[fcjack]

What this PR does / why we need it:

Since we are using the distroless docker image, we don't have shell and tools to execute the healthcheck when starting loki.
For some cases we can run a sidecar, kube is calling the ready endpoint.

But in cases that are not these two, like docker swarm, it is not possible to make a check.

So we are adding a health command support to the binary, where the user can call the binary with the -health arg, this will make Loki check itself without any external dependency or shell needed in docker container.

Which issue(s) this PR fixes:
Fixes #20149

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

[dragonsahead]

Pardon my interruption here, I can't see any releases where this PR is included, am I wrong?

[JStickler]

@dragonsahead Loki 3.6 went out in November. This PR should be released as part of Loki 3.7.

[dragonsahead]

Thanks @JStickler I thought this was already there on a minor release of 3.6

[loki-gh-app]

The backport to release-3.6.x failed:

Reviews may only be requested from collaborators. One or more of the users or teams you specified is not a collaborator of the grafana/loki repository.

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-20313-to-release-3.6.x origin/release-3.6.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x ef69cfd97cf1d5bd58758952cbc3eb48a99d060e

When the conflicts are resolved, stage and commit the changes:

git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Push the branch to GitHub:
git push --set-upstream origin backport-20313-to-release-3.6.x
# Create the PR body template
PR_BODY=$(gh pr view 20313 --json body --template 'Backport ef69cfd97cf1d5bd58758952cbc3eb48a99d060e from #20313{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title 'feat: add loki health command (backport release-3.6.x)' --body-file - --label 'size/L' --label 'type/bug' --label 'backport' --base release-3.6.x --milestone release-3.6.x --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# Push the branch to GitHub:
git push --set-upstream origin backport-20313-to-release-3.6.x

# Create a pull request where the `base` branch is `release-3.6.x` and the `compare`/`head` branch is `backport-20313-to-release-3.6.x`.

# Remove the local backport branch
git switch main
git branch -D backport-20313-to-release-3.6.x