Today, when the pass infra schedules a pass/nested-pipeline on a set of
ops, it exits early as soon as it fails on one of the ops. This leads to
non-exhaustive, and more importantly, non-deterministic error reporting
(under async).
This PR removes the early termination behavior so that all ops have a
chance to run through the current pass/nested-pipeline, and all errors
are reported (async diagnostics are already ordered). This guarantees
deterministic & full error reporting. As a result, it's also no longer
necessary to -split-input-file with one error per split when testing
with -verify-diagnostics.
5b21fd298c