This reverts commit 98927ea5.

Reason for revert: Breaks Mac GC Stress bot.
https://uberchromegw.corp.google.com/i/client.v8/builders/V8%20Mac%20GC%20Stress/builds/13299/steps/Mjsunit/logs/for-await-of

Original change's description:
> [ignition] Be smarter about register allocation in VisitSuspend
> 
> Split BytecodeGenerator::VisitSuspend into two pieces, one for
> building the suspension code and one for resumption (these
> are split into separate Build methods for convenience).
> Each gets its own RegisterAllocationScope, which allows us to
> reduce the register file size of the empty generator by 1.
> 
> For consistency, rename VisitGeneratorPrologue() to
> BuildGeneratorPrologue() to match the names of the two
> newly-created methods.
> 
> Bug: v8:6379
> Change-Id: I08a617a44f99706cfff09bf86fb0a25a9cd6e032
> Reviewed-on: https://chromium-review.googlesource.com/503593
> Commit-Queue: Adam Klein <adamk@chromium.org>
> Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#45318}

TBR=rmcilroy@chromium.org,adamk@chromium.org,neis@chromium.org,kozyatinskiy@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
Bug: v8:6379

Change-Id: I787fc3811c4f33a8021cf9170d43a74ed9b55d1c
Reviewed-on: https://chromium-review.googlesource.com/506548Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45319}