test: Pre-compile common wheels in base test env (#13715)

The test suite disables Python bytecode caching so if we don't
pre-compile the bytecode for coverage, setuptools, and pytest-subket
which are all preinstalled in the test environments, we pay a heavy
import time penalty (e.g., setuptools during a PEP 517 build). pip is
already pre-compiled, FWIW.

This is doubly bad for coverage and pytest-subket since they are
imported on every Python process startup.

Locally, this shaves a full minute from a full test suite run down to
2:45 from 3:45.

Author: ichard26

tests/conftest.py

@@ -420,6 +420,7 @@ def _common_wheel_editable_install(
                 },
                 interpreter=sys.executable,
                 script_kind="posix",
+                bytecode_optimization_levels=[0],
             ),
             additional_metadata={},
         )