feat: move metric aggregation to a per-tenant config

[trevorwhitney]

What this PR does / why we need it:
This moves the metric aggregation feature flag to a per-tenant config

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

[loki-gh-app]

This PR must be merged before a backport PR will be created.

[benclive]

Could/should we default this to true?

[trevorwhitney]

It would make the deployment easier. My big concern is the surprise for OSS users, as I'd still consider it a beta/experimental feature.

[loki-gh-app]

The backport to k226 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-14709-to-k226 origin/k226
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x c1fde26730b4fc54e4bbc724d1b29f653541f720

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-14709-to-k226
# Create the PR body template
PR_BODY=$(gh pr view 14709 --json body --template 'Backport c1fde26730b4fc54e4bbc724d1b29f653541f720 from #14709{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title 'feat: move metric aggregation to a per-tenant config (backport k226)' --body-file - --label 'size/L' --label 'type/docs' --label 'product-approved' --label 'backport' --base k226 --milestone k226 --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-14709-to-k226

# Create a pull request where the `base` branch is `k226` and the `compare`/`head` branch is `backport-14709-to-k226`.

# Remove the local backport branch
git switch main
git branch -D backport-14709-to-k226