`test_runner` command line doesn't allow running scripts with parameters #14791

The following code is in test_runner.py:

         # Individual tests have been specified. Run specified tests that exist
         # in the ALL_SCRIPTS list. Accept the name with or without .py extension.
         tests = [re.sub("\.py$", "", test) + ".py" for test in tests]

This adds .py to the end of the test name, making it impossible to run, say rpc_bind.py --ipv6. This test was failing here locally so I wanted to run it separately.

I think this step should be skipped if .py is already given. Or alternatively, only applied to the first part of the test name and not arguments.