Display/note error messages when builds fail in the collector

[Mark-Simulacrum]

Currently we just don't have any pstat values for builds that failed in the collector, like for https://perf.rust-lang.org/compare.html?start=98a5a98f44130b5bafb4f2b2f3126fb22a5a3228&end=9dcfdc218c68c3bb7a32f219622672a50996a459. That looks pretty confusing to users, so we should try to avoid this kind of UI.

We can likely check the error table for the base & next commits unconditionally on all the series we're querying and put links or something in to the error message when running that benchmark. Surfacing this at the top of the page for any benchmarks which stopped compiling is likely particularly critical on e.g. try builds, since otherwise that information seems likely to be pretty hidden (and we'd end up landing breakage onto master).