FastAPIInstrumentor.uninstrument_app() doesn't remove the app from the static list of instrumented apps, causing memory leaks

[brianmedigate]

Describe your environment

OS: Ubuntu 22.04
Python version: Python 3.11.11
Package version: 0.45b0

What happened?

Calling FastAPIInstrumentor.uninstrument_app() doesn't remove the app parameter from the _InstrumentedFastAPI._instrumented_fastapi_apps set. If instrumenting and uninstrumenting is done repeatedly, for example in a test suite, this can lead to leaking significant amount of memory.

Steps to Reproduce

import sys

from fastapi import FastAPI
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor

app = FastAPI()
print(sys.getrefcount(app))
FastAPIInstrumentor.instrument_app(app)
print(sys.getrefcount(app))
FastAPIInstrumentor.uninstrument_app(app)
print(sys.getrefcount(app))

Expected Result

After the call to uninstrument_app() the refcount should be the same as it was before calling instrument_app()

Actual Result

The refcount is one greater.

Additional context

The mechanism of storing references to the apps was implemented in #1258.

Would you like to implement a fix?

Yes

[brianmedigate]

@TheAnshul756 @sanketmehta28 @srikanthccv

[pvital]

@xrmx, could you please assign this one to me? TIA.

[rahulhacker]

@xrmx : in case if no one is working, can you please assign to me.