[3.14] gh-158618: Split test_free_threading into per-module tests to avoid timeouts (GH-158620) (#158662)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: miss-islington

Lib/test/libregrtest/findtests.py

@@ -21,6 +21,7 @@
     "test_asyncio",
     "test_concurrent_futures",
     "test_doctests",
+    "test_free_threading",
     "test_future_stmt",
     "test_gdb",
     "test_inspect",