This brings in
third_party/inspector_protocol/encoding/encoding_test.cc
from the upstream project and makes it work for v8's
unittest suite.

encoding_test_helper.h is a V8 specific implementation,
which delegates to src/inspector/v8-string-conversions{.h,.cc},
for the utf8 / utf16 conversion routines.

I'm also fixing / updating roll.py, for future rolls.

Change-Id: I08e4784838ff81ef3ac328f783512b42c91b6bcd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1597215Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61393}