Add the necessary V8_EXPORT_PRIVATE attributes and a few other minor
changes to make building DLLs with MSVC happy. (Note: Debug builds still
seem to be failing in Torque, but this fixes Release builds).

Bug: v8:8791
Change-Id: Ia4d5372fd1cb961e6268a2b5c089bcd17822f1e5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1996157Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65822}