This also adds support in the c1 visualizer output generator to resolve
splintered live ranges before they have been merged back in.

Bug: v8:8238
Change-Id: I61e5f6da2e8b77ca9b42fae9004c77163d11960f
Reviewed-on: https://chromium-review.googlesource.com/c/1270817Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56595}