Consolidate pendulum usage in prefect.server.services

[desertaxle]

Related to #16910

[codspeed-hq]

CodSpeed Performance Report

Merging #17100 will not alter performance

_{Comparing remove-pendulum-from-services (622a463) with main (955378c)}

Summary

✅ 2 untouched benchmarks

[zzstoatzz]

nice!

just to make sure im understanding, you're using - timedelta(...) instead of subtract intentionally to avoid coupling ourselves to the pendulum API right? and the typing for that works out fine?

[desertaxle]

you're using - timedelta(...) instead of subtract intentionally to avoid coupling ourselves to the pendulum API right?

Yup, I'm trying to avoid using pendulum specific methods on DateTime wherever I can.