This reverts commit f6d73509.

Reason for revert: Perf regressions https://crbug.com/758126

Original change's description:
> [csa] Refactor large-object handling in string allocation
> 
> CSA::AllocateSeq{One,Two}ByteString used its own home-grown handling to
> allocate very large strings. This CL refactors both methods to use
> AllocationFlags::kAllowLargeObjectAllocation instead. Callers now need
> to specify explicitly if large-object allocation is possible or not.
> 
> Bug: chromium:636391
> Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
> Change-Id: I0b7ffb0b083f4e977cea42c500f8f2ee1c60519f
> Reviewed-on: https://chromium-review.googlesource.com/625738
> Reviewed-by: Camillo Bruni <cbruni@chromium.org>
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47504}

TBR=cbruni@chromium.org,jgruber@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:636391
Change-Id: Iab88ce400f489a677df821d4053bd3678289ae2e
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/637392Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47639}