Deletion can cause collisions to be moved in the map which breaks iteration.
For now just remove this support. Also add some additional collision tests
to the test.

BUG=v8:5203

Change-Id: I54a0a4af51da08b3f963dc1d7661dba291e4efea
Reviewed-on: https://chromium-review.googlesource.com/445900Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43621}