gh-158618: Split test_free_threading into per-module tests to avoid timeouts (#158620)

Author: hugovk

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",