Effect-control-linearizer will update a basic block to connect it
directly to the end node if it has an Unreachable node. Usually the
block would already have been connected directly to end (via a Throw
node) already, however in some cases it can be connected indirectly
(via a branch, where both end in a throw node).

If this happens, and the Effect-control-linearizer is maintaining the
schedule (e.g., for TurboProp), it will cause the end block to have
unreachable predecessor blocks, which can cause issues with the
register allocator.

To fix this, have the BasicBlockUpdater remove all successor blocks
from the schedule, when they become Unreachable. Also add some tests
to cover this in effect-control-linearizer-unittests.

BUG=v8:10332,v8:9684

Change-Id: Ibce140e6d1f61751a86247e6f8c36075723a1e55
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2120537
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66994}