Vendor mozdebug and stop using distutils (#30659)

The version of `mozdebug` installable via pip is two years old and
Mozilla is slow to release new versions. It also uses `distutils` which
doesn't work on newer Python versions. Vendor it and stop using
`distutils` there.

python/mach_bootstrap.py

@@ -20,6 +20,7 @@ WPT_SERVE_PATH = os.path.join(WPT_PATH, "tests", "tools", "wptserve")
 
 SEARCH_PATHS = [
     os.path.join("python", "mach"),
+    os.path.join("third_party", "mozdebug"),
 ]
 
 # Individual files providing mach commands.