The plan is to eliminate the DecompressionElimination reducer
as well as the Compressed representation. We are adding a flag to
easily swap between the old system and the new one.

Bug: v8:7703, v8:9206
Change-Id: I083fc7a835962eddfd60e9c403131587489f4632
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1815134
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64185}