[M126][compiler] Clear stale data for ZeroExtendsWord32ToWord64

The first call to ZeroExtendsWord32ToWord64 produces a correct result,
but leaves some incorrect values in phi_states_. To avoid incorrect
behavior, we should clear those values when starting anew.

I think that the performance impact of this change on compilation time
should be small, because calls to ZeroExtendsWord32ToWord64 are
infrequent. Here is a histogram showing, per function compiled in
Octane, how often this new code is run:

0: 74.7%
1: 13.1%
2: 6.3%
3: 2.5%
4 or 5: 1.7%
6 to 9: 0.9%
11 to 33: 0.8%

Bug: 356196918
Change-Id: I00a9e74652025bf8a32cb083a6e01c0273e44043
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5766478
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#95528}
(cherry picked from commit 780d5608bb8ab63a3cd4b5c4846a3ec41e21c1a8)
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5803612
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Roger Felipe Zanoni da Silva (xWF) <rzanoni@google.com>
Auto-Submit: Roger Felipe Zanoni da Silva (xWF) <rzanoni@google.com>
Reviewed-by: Seth Brenith <seth.brenith@microsoft.com>

• src/compiler/backend/instruction-selector.cc[diff]

    fetch v8

    git pull origin
    gclient sync

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*