This is a reland of c924f54e

Reason: Added back a bitcast that was supposed to be redundant (but it
wasn't)

Changes can be seen from patchets 1..3.

Original change's description:
> [turbofan][ptr-compr] Remove redundant ChangeTaggedToCompressed
>
> The final goal is to eliminate it altogether. This CL just
> eliminate the redundant ones.
>
> Bug: v8:7703
> Change-Id: If6e718c373fca7c65ce46c347533ec4550fbc444
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1950968
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#65398}

Bug: v8:7703
Change-Id: I099e67d0255d4ad5529a73b272df893069374136
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1965582Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65454}