pytester: avoid unraisableexception gc collects in inline runs to speed up test suite (#13525) (#13526)
Because `pytester.runpytest()` executes the full session cycle (including
`pytest_unconfigure`), it was calling `gc.collect()` in a loop multiple
times—even for small, fast tests. This significantly increased the total
test suite runtime.
To optimize performance, disable the gc runs in inline pytester runs
entirely, matching the behavior before #12958.
Locally the test suite runtime improved dramatically, dropping from 425s
to 160s.
Fixes #13482.
(cherry picked from commit 391324e13a6589f5d824d053240d4b9a4139a115)
Co-authored-by: Ran Benita <ran@unusedvar.com>
Co-authored-by: Bruno Oliveira <bruno@soliv.dev>