[heap] Reland "Remove size specializations in static object visitors. (patchset #4 id:60001 of https://codereview.chromium.org/2763413007/ )"

This reverts commit 61df2d90.
The CL was speculatively reverted due to canary crashes, which turned
out to be caused by another CL.

Original issue's description:
> [heap] Remove size specializations in static object visitors.
>
> Apart from that this patch adds kVisitJSObjectFast for JSObjects that
> do not have any unboxed double fields and can be visited without
> run-time layout check.
>
> BUG=chromium:694255
>
> Review-Url: https://codereview.chromium.org/2763413007
> Cr-Commit-Position: refs/heads/master@{#44237}
> Committed: https://chromium.googlesource.com/v8/v8/+/dbb1cbe3a85d5c5528ce876d905e78d2ab35f00b

Review-Url: https://codereview.chromium.org/2808533002
Cr-Commit-Position: refs/heads/master@{#44494}