Currently the SourcePositionTableBuilder requires a Zone because it
holds a ZoneVector<byte> of the encoded entries. Since ZoneVector is a
suboptimal data structure anyway, and for Liftoff we don't even have a
Zone allocated currently, this CL replaces the ZoneVector by
std::vector.

R=mstarzinger@chromium.org

Bug: v8:6600
Change-Id: I8010143e917e2351664e2b53746753b597f4407a
Reviewed-on: https://chromium-review.googlesource.com/779181Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49534}