Allow CLI to be invoked with python -m prefect

[sky-code]

Added main module to prefect package to be able to use prefect cli with python -m prefect ... approach.

[codspeed-hq]

CodSpeed Performance Report

Merging #16790 will not alter performance

_{Comparing sky-code:main (39a311b) with main (e047607)}

Summary

✅ 2 untouched benchmarks

[desertaxle]

Thanks for opening a PR, @sky-code! Could you provide a bit more information on why this change is needed?

[sky-code]

Thanks for opening a PR, @sky-code! Could you provide a bit more information on why this change is needed?

It primarily enables better integration with certain tools. For instance, this approach allows you to easily use PyCharm’s run configurations to execute Prefect CLI commands, such as:

[jbw-vtl]

By chance opened essentially the same PR as ran into a similar use-case which would benefit from being able to use python -m prefect.

being able to integrate prefect into PyCharm ruin configuration also simplifies the setup required to debug the prefect cli / server

[desertaxle]

Thanks for the Pr and explanation @sky-code, and thanks @jbw-vtl for separately raising a similar PR!