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.