This CL extracts some functionality from inspector-test.cc to be reused
by the inspector fuzzer.

It also puts all functions in the v8::internal namespace, and adds
separate functions in v8::internal to be called by ::main such that
we have direct access to the full namespace there.

R=szuend@chromium.org

Bug: chromium:1142437
Change-Id: I671317822bdc1c721334469811893affcc460f8f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2501847Reviewed-by: Simon Zünd <szuend@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70821}