Move fast/parser/xml-bad-encoding to wpt

I added this test to fast/ without thinking about it, and it got flagged
for being a new test not in wpt.

The -crash.html should make wpt recognize it as a "crash test":
https://web-platform-tests.org/writing-tests/crashtest.html

Change-Id: Ia424f0f407dba48b0a7bf87331a6843fb3b13e39
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2231867
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775791}