Filter warnings from AssertionRewritingHook when exec'ing module

[Redoubts]

This method raises warnings from packages very early in the pytest collection process, way before configured filterwarnings can be set up. It's not interesting to raise anything here IMO, so let's filter and ignore them.

This should also prevent spurious issue reports for you, like #11741 and #9884

[Redoubts]

Basically this solves spam issues like:

% pytest some_test.py

<venv>/lib/python3.11/site-packages/_pytest/assertion/rewrite.py:178: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
  exec(co, module.__dict__)
<venv>/lib/python3.11/site-packages/pkg_resources/__init__.py:2832: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('sphinxcontrib')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
  declare_namespace(pkg)
============================================= test session starts =============================================
platform linux -- Python 3.11.9, pytest-8.1.1, pluggy-1.4.0
...

It's not really impacting functionality, but it's annoying spam and sometimes the packages ultimately causing this have no fixes to pick up

[The-Compiler]

If I'm reading this correctly, this causes any warnings at import time to be silenced completely?

If so, that definitely doesn't seem desirable to me. We should definitely improve our reporting to point out where they actually happen, maybe even make them filterable (say, maybe by catching and reraising them?), but silently suppressing them in a test runner of all places definitely isn't the thing to do.