This is a reland of e38cb757. This
was reverted as a potential culprit for a wasm failure. The
actual revert that fixed the bots is here:
https://chromium-review.googlesource.com/c/v8/v8/+/2630736.
This should be safe to reland. I verified locally that the test is
failing with or without this change.

Original change's description:
> [turboprop] Enable tierup to TurboFan with FLAG_turboprop
>
> FLAG_turboprop was used to test the turboprop compiler without any
> further tierup to TurboFan. This cl changes:
> - FLAG_turboprop to also tier up to TurboFan.
> - Introduces FLAG_turboprop_as_toptier to continue running the
>   configuration without tierup.
> - Removes FLAG_turboprop_as_midtier which is same as FLAG_turboprop.
>
> Bug: v8:9684
> Change-Id: I487bda13d226434837770ecc43b3ced7c31ccf19
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2622214
> Commit-Queue: Mythri Alle <mythria@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#72101}

Bug: v8:9684
Change-Id: I8b61fd8e562190c3c7bf5a003273f2a058542dad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2632588
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72110}