Keep the existing method for compatibility, by converting
to json from CBOR using the inspector_protocol_encoding library,
via a v8 specific interface library that directs routines for
converting between strings and doubles to v8's implementations.

This change also brings in the encoding.h / encoding.cc files from the
upstream inspector_protocol project. The only modification here
are the header guards, and the namespace. I will fix roll.py to
make it so that we pick up future changes.

third_party/inspector_protocol/BUILD.gn is specific to v8, by necessity.
third_party/inspector_protocol/.clang-format is a copy of the upstream
file. If we don't put this, we'll find ourselves auto-formatting the roll,
which is annoying.

Change-Id: I20fa8759164e7a39f8a7c30e0d2a3f8a7e4be227
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1590627Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61187}