fix: Remove pytest-asyncio dependency and fix more resource warnings #4435

Job	Run time
mypy	53s
pyright	38s
slotscheck	16s
Test server integration (uvicorn<0.27.0)	40s
Test Minimal Application with Base Dependencies	20s
Test Minimal Pydantic 1 application	17s
Test server integration (uvicorn>=0.27.0)	36s
test-platform-compat	0s
validate	11s
test (3.10) / test	1m 39s
test (3.12) / test	1m 51s
test (3.11) / test	1m 35s
test (3.9) / test	1m 41s
test (3.8) / test	1m 52s
build-docs	0s
upload-test-coverage	0s
codeql	0s
sonar	0s
	12m 29s

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