Fix fastapi example test not working and make deps raise SolverProblemError.

[waketzheng]

Description

Fix these issues: #1246 #1029

Motivation and Context

I got the SolverProblemError yesterday and fix it by make up
The latest version of fastapi recomment to use anyio/httpx for async test:
https://fastapi.tiangolo.com/advanced/async-tests/
And use asgi-lifespan for tortoise init db and close connections when testing

How Has This Been Tested?

make test worked as expected
cd examples/fastapi && PYTHONPATH=. pytest _tests.py worked too

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed. make test worked.

[long2ice]

Thanks!