Send worker metadata with first heartbeat

[abrookins]

Send worker metadata with the first worker heartbeat. For now, this metadata includes the Prefect integrations installed in the current process.

NOTE: This PR only sends the data if we're connected to Cloud. Support for open-source Prefect servers will follow.

Closes CLOUD-542.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
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[codspeed-hq]

CodSpeed Performance Report

Merging #15898 will not alter performance

_{Comparing cloud-542-worker-metadata (329c093) with main (d332172)}

Summary

✅ 3 untouched benchmarks

[desertaxle]

LGTM!

I left one suggestion to send the prefect version with the heartbeat in service of #12126, but feel free to punt on that for now and we'll come back to it.

[abrookins]

Good suggestion! Here was my thinking on excluding it. Currently, the client already sends its version in an HTTP header, so we're capturing it that way to store in metadata server-side in the heartbeat endpoint. Does that work? We'll plan to port that to open-source when we bring the feature over.

[desertaxle]

Good suggestion! Here was my thinking on excluding it. Currently, the client already sends its version in an HTTP header, so we're capturing it that way to store in metadata server-side in the heartbeat endpoint. Does that work? We'll plan to port that to open-source when we bring the feature over.

Yeah, that makes perfect sense to me!