Remove the unnecessary int64_t version of RoundNumberToIncrement
and remove the unneeded RoundHalfAwayFromZero. Change the type of the
increment to double from int64_t.
split from cl/3750098

Bug: v8:11544
Change-Id: I591486c472e9c1343306ff9a1d0384d06fe01835
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3824194
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82403}