Enable x509 ca and req tests on Windows

- Use absolute paths with forward slashes for all temp files via
  _tmp() helper so wolfSSL recognizes them correctly
- Use explicit UTF-8 encoding with LF newlines when writing config
  files so wolfSSL's NCONF_load can parse them on Windows
- Remove $dir variable expansion in config templates; use direct
  absolute paths to CERTS_DIR instead
- Pass bare filenames to ca -out (not absolute paths) since wolfSSL
  prepends new_certs_dir and doesn't recognize drive-letter paths
  as absolute
- Export PROJECT_ROOT from wolfclu_test.py for test file path helpers

Author: julek-wolfssl

tests/wolfclu_test.py

@@ -8,6 +8,7 @@
 
 _TESTS_DIR = os.path.dirname(os.path.abspath(__file__))
 _PROJECT_ROOT = os.path.dirname(_TESTS_DIR)
+PROJECT_ROOT = _PROJECT_ROOT
 
 
 def _find_wolfssl_bin():