feat(metrics): add additionalServiceMonitors option

[swiatekm]

Add sumologic.metrics.additionalServiceMonitors, which works the same way as the respective kube-prometheus-stack option, but without depending on Prometheus to be enabled.

Checklist

• Changelog updated or skip changelog label added
• Documentation updated
• Template tests added for new features

[swiatekm]

This isn't a breaking change, and I'd like to merge it to v3 as well to make migration easier for users. I'll put up a separate PR for the v4 migration doc.

[sumo-backporter]

The backport to release-v3 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 working tree
git worktree add .worktrees/backport-release-v3 release-v3
# Navigate to the new working tree
cd .worktrees/backport-release-v3
# Create a new branch
git switch --create backport-3292-to-release-v3
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 20516028f183ce1fe260a34e7f07835aceea64fb
# Push it to GitHub
git push --set-upstream origin backport-3292-to-release-v3
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-v3

Then, create a pull request where the base branch is release-v3 and the compare/head branch is backport-3292-to-release-v3.