"By my deeds I honor him. V8."

- Add basic build files for library and unittests.
- Integrate unittests also in existing V8 unittests for simplicity.

The CL also adds FinalizerTrait and unittests to allow building a
testing target that executes code.

FinalizerTrait is used to determine how managed C++ types are
finalized. The trait should not be overridable by users but needs to
be exposed on API-level to avoid including library-internal headers.

Bug: chromium:1056170
Change-Id: I64d91053410a17a7835e50547f58990625d2da28
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2108549Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66834}