This PR makes `#guard_msgs` to treat `trace` messages separate from
`info`, `warning` and `error`. It also introduce the ability to say
`#guard_msgs (pass info`, like `(drop info)` so far, and also adds
`(check info)` as the explicit form of `(info)`, for completeness.
Fixes#8266
This PR allows simp dischargers to add aux decls to the environment.
This enables tactics like `native_decide` to be used here, and unblocks
improvements to omega in #5998.
Fixes#7318