Adds reduction case in MachineOperatorReducer for when the left-hand side of a
Word64Equals is based on a 64-bit shift-and-mask operation, as is the case
when Torque accesses 64-bit bitfields.

This improves Speedometer2 by 0.15% on a Neoverse-N1 machine, with
React-Redux being improved by 0.4%.

Change-Id: Icd0451c00c1b25f7d370e81bddcfd668a5b2523c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3834027
Commit-Queue: George Wort <george.wort@arm.com>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82593}