This is a reland of f589d561

Now with an ASAN-container-overflow false positive workaround:
Somehow ASAN was unhappy about a simple
std::vector<std::string>::push_back.
Increasing the std::vector capacity before doing the push_back
strangely fixes the problem.

Original change's description:
> [torque] move class tests to unittests
>
> This avoids the generation of fake external classes.
>
> Bug: v8:7793
> Change-Id: I9744b299d3ec474d72b298b4f6143f95e345d1d9
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1625991
> Reviewed-by: Simon Zünd <szuend@chromium.org>
> Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#61778}

TBR: szuend@chromium.org, sigurds@chromium.org
Bug: v8:7793
Change-Id: Ifa1958e4d6e850ba27632aa95c7efaf5ca4bfefa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627970
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61807}