[3.12] gh-109615: Fix test_tools.test_freeze SRCDIR (#109935) (#109950)

[3.12] gh-109615: Fix test_tools.test_freeze SRCDIR (#109935) (#109950)

gh-109615: Fix test_tools.test_freeze SRCDIR (#109935)

Fix copy_source_tree() function of test_tools.test_freeze:

* Don't copy SRC_DIR/build/ anymore. This directory is modified by
  other tests running in parallel.
* Add test.support.copy_python_src_ignore().
* Use sysconfig to get the source directory.
* Use sysconfig.get_config_var() to get CONFIG_ARGS variable.

(cherry picked from commit 1512d6c6ee2a770afb339bbb74c1b990116f7f89)