Fix load_flow_argument_from_entrypoint to work with async flows

[elisalimli]

Fixes #13765

The load_flow_argument_from_entrypoint function in Prefect doesn't support finding async functions (AsyncFunctionDef) decorated with @flow.

What We Expect:
It should be able to find both async functions and regular functions (FunctionDef) decorated with @flow.

[serinamarie]

Hi @elisalimli thanks for opening your first PR to prefect! Giving the workflows a run now, and I think @desertaxle would probably be the best one to take a final look at this :)

Update: You probably want to install pre-commit hooks. Please see our contributing guide.

[desertaxle]

Thanks for the PR @elisalimli! Could you please add a test case to cover this case?

[elisalimli]

Thanks for the quick response @desertaxle and @serinamarie.

@desertaxle I have added a test case in 60b5602

[zzstoatzz]

lgtm!

cc @desertaxle

[elisalimli]

This issue blocks us as a team right now, therefore we would be glad if you could merge within today/tomorrow. Thanks in advance!

cc @zzstoatzz @desertaxle @serinamarie

[aaazzam]

Likely related to #13765

[desertaxle]

Thanks!