[JHeilCoveo]

What

Fix cachetools' decorators by using IdentiyFunction. I based this PR off #5482.

Why

This simple code currently fails

from cachetools.func import ttl_cache


@ttl_cache(ttl=1)
def simple(a: int) -> int:
    return a + 1


if __name__ == "__main__":
    print(simple(1))

With following error messages :

simple.py:12: error: Argument 1 has incompatible type "Callable[[int], int]"; expected
simple.py:18: error: not callable

Fixes #5617