Currently, run.py will parse only the args it knows about, and basically ignore everything else: https://chromium.googlesource.com/chromium/src/+/0f5696102a244ef87825997ad22d470655232256/ios/build/bots/scripts/run.py#195

This results in silent failures when the arguments are incorrect, and it already bit me twice:

Missing a comma between argument strings: https://bugs.chromium.org/p/chromium/issues/detail?id=794614#c18 (wasted half a day looking for the bug)

Incorrect order of arguments didn't result in any visible failures:
 https://crrev.com/i/531570

I'd like to convert the script from parse_known_args() to just parse_args() which will fail on unknown arguments. It prevents giving test_args as command-line arguments, but those are never used anyway, and these arguments are always provided through --args-json string from the recipes.