Adds support to render the live ranges as ascii diagram. This is
similar in nature to what the c1visualizer would produce.

Also, print the visualization when tracing the register allocator.

Change-Id: Ib6a43f67ba356e9a80cacaddfdbd6d589c685483
Reviewed-on: https://chromium-review.googlesource.com/c/1346114Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57687}