test: rename WPT console test

test-console-is-a-namespace.js is a WPT Console test. It is the only
WPT Console test file that we have that doesn't start with
`test-whatwg-`. Rename it to test-whatwg-console-is-a-namespace.js
so that WPT tests can be found relatively easily. Just as it is useful
to separate the WPT URL tests from our URL tests, it will likely be
useful to separate our Console tests from WPT Console tests if we add
more WPT Console tests (which I hope we do).

PR-URL: #23340
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>