This CL adds the i32.trunc_s:sat/f32 WASM opcode to the turbofan
compiler and interpreter (more saturating operators will be added in
later CLs).

The operatation has been added under an experimental flag.

Bug: v8:7226
Change-Id: Ia69e981ffddb2da682e53ba25f489fc9d0cd2db5
Reviewed-on: https://chromium-review.googlesource.com/834670
Commit-Queue: Karl Schimpf <kschimpf@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50311}