csharp: fix some unit tests that rely on garbage collection

csharp: fix some unit tests that rely on garbage collection

Summary:
Fix unit tests `TestEoInherit.inherited_collected` and
`TestFunctionPointers.set_callback_inherited_called_from_c`.

Iterate through garbage collection and EFL main loop more times to ensure that
allocated objects are really collected.

Also expand the test utility method `CollectAndIterate` to receive the number of
times to call the whole cleaning iteration process (not only the garbage
collection).

Test Plan: `meson test`

Reviewers: lauromoura

Reviewed By: lauromoura

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9271