This CL adds a mode to the JSReceiver::GetDataProperty that does
not box unboxed double fields. This method can be used to fix a critical
bug in the heap snapshot generator that currently causes a GC in a place
where no GC should be caused.

Change-Id: If195f6811090281d364e3c8fa221a1d6b96bcd80
Bug: v8:9993
Fixed: chromium:1038490
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1993286
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65694}