Mock every usage of is_faker_function to speed up the unit tests

[R-Palazzo]

Problem Description

The initial call of is_faker_function from RDT is consistently slow, taking a few seconds. When running the unit tests, the test that makes this first call always takes longer, causing the unit test to run slowly.

Expected behavior

Running the unit test should take almost no time.
Whenever the is_faker_function method is utilized, tests should mock it with the correct return values, whether used directly or indirectly.

Additional context

To detect which test is doing the first is_faker_function call, one can run:
pytest tests/unit --duration=0
It will be the test that takes more time.