Sync grafana/agent:c6fbc923 into grafana/alloy:main

[rfratto]

Process for which I did this:

git remote add grafana-agent [email protected]:grafana/agent.git 
git fetch grafana-agent main 
git checkout -b sync-grafana-agent 
git merge grafana-agent/main 
# (fix merge conflicts)
git commit  

[rfratto]

This is going to be merged via a squash commit, which I think means we'll come across the same exact merge conflicts every single time we do this.

There's probably an argument for these sync PRs to be merged via actual merge commits, but I'd like to play around with our existing behaviour (squashing) a few more times before we entertain merge commits.