Fix and re-enable the flexible representation for Math.floor (which is used to
implement Math.ceil) and Math.round, which allows Math.floor and Math.round to
return double results instead of int32, and therefore allows values outside
the int32 range, especially -0 is now a valid result, which doesn't deopt.

Also port this feature to x64 and ia32 when the CPU supports the SSE4.1
extension.

This addresses all the known deoptimization loops related to Math.round
in the Kraken benchmark suite, and seems to also address most of the
deoptimization loops related to Math.floor in the Oort Online benchmark.

Drive-by-fix: Import the regression tests for the broken HMathFloorOfDiv
optimization that caused the initial revert of the feature (for arm64 only
back then).

BUG=chromium:476477,v8:2890,v8:4059
R=jarin@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1841513003

Cr-Commit-Position: refs/heads/master@{#35094}