Review Mojo's priorities

• I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

std.testing._assert_aborts landed in as a first pass replacing the old -D test=N + lit RUN-line pattern for testing aborting code. It works, but we punted on a few rough edges to get it merged.
As notes in the initial implementation "there's a lot of potential for TOCTOU type issues and deadlocks... we should create follow-up issues to properly redirect things".

What is your motivation for this change?

Tracking issue for those improvements.

Any other details?

No response