Prefect yaml triggers add description.

[jeanluciano]

Adds the description to automations from triggers specified in the prefect.yaml.

closes: #16655

Checklist

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[codspeed-hq]

CodSpeed Performance Report

Merging #16944 will not alter performance

_{Comparing jean/oss-6107-propagate-trigger-descriptions-from-prefect-yaml (bc87d01) with main (20b074c)}

Summary

✅ 2 untouched benchmarks

[cicdw]

nice! could you add one more test that confirms the description makes it to the API? (or augment an existing test)

[cicdw]

These only test the description is included in the client-side payload sent to the server, they don't test that the server receives and stores the description; maybe adding a non-trivial description field to this test would do the trick: https://github.com/PrefectHQ/prefect/blob/main/tests/events/server/models/test_automations.py#L176