Feedback pollution can create situations in which we statically see stores to the same field with incompatible representations; dynamically this should be impossible for a single TurboFan compilation unit. Instead of failing an assertion we produce Unreachable nodes.

R=tebbi@chromium.org

Bug: chromium:967434 chromium:967506
Change-Id: Id549ec84f28b4fed2d2e5ef05b40b48bc5b30e97
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1632169
Commit-Queue: Georg Schmid <gsps@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61894}