Expose "Report issue" next to audit/gather failures.

[paulirish]

Now that we catch all non-fatal errors, it means that any exception during a gatherer or audit is caught and the user doesn't get the sweet github buildReportErrorLink() action.

One option is we could surface such a link next to the red debugString in the report, to let the user file any bug leading to this error state.

This is a decent compromise until we have exception tracking in the wild.

[vinamratasingal-zz]

Closing in favor of the umbrella issue.