This is a reland of 6f763280

Original change's description:
> [cleanup] Cleanup handling of padding field in Map
> 
> Bug: v8:8834
> Change-Id: Iae9cbcccb8747298c5680ac1e865efebee85acec
> Reviewed-on: https://chromium-review.googlesource.com/c/1480385
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59774}

Bug: v8:8834
Change-Id: I6a3b436984a7a412f07bb66647864472a134d264
Reviewed-on: https://chromium-review.googlesource.com/c/1482914Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59793}