R1:3d3fff4991ab

Fix weird remarkup linewrapping on a few instructions forms, plus move toward fixing Phame/CORGI remarkup issues

Summary:
Fixes T10381. When we converted to `PHUIRemarkupView`, some instructional text got linebreaks added when it shouldn't have them (the source is written in PHP and wrapped at 80 characters, but the output should flow naturally).

Fix this so we don't preserve linebreaks.

This also makes `PHUIRemarkupView` a little more powerful and inches us toward fixing Phame/CORGI remarkup issues…