The SourcePositionTableBuilder unconditionally allocates heap memory for
every Liftoff compilation. This shows up with 1-2% of compilation time
in profiles. Hence move the vector contained in the
SourcePositionTableBuilder into the compilation zone. Such a zone
already exists for both Liftoff and TurboFan, so we can easily save
allocations this way.

R=thibaudm@chromium.org

Bug: v8:10576
Change-Id: Ia83d05cc8c36c775ebff6ec2064e9c3f8cc4d384
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2224221
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68112}