Additional change: Add ValueType::is_bottom()

Change-Id: I8e294c6318b6e51efac0a07ac0ec059ea9dc5654
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2440515
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70243}