Libs team meetings: Track regressions and critical issues

[m-ou-se]

In our libs meetings, we should make sure to track and respond to issues tagged as high/critical priority, or as regressions, such as rust-lang/rust#85667 and rust-lang/rust#85694. For the T-libs label, nobody is doing this right now. For the T-libs-impl label, the compiler team handles this right now, but we should take that over, in our new (non-api) meetings.

(We should probably change the first label to T-libs-api too.)