Don't log panics from proc macros

[matklad]

see https://users.rust-lang.org/t/reproducing-a-rust-analyzer-failure-in-the-terminal/63459/7?u=matklad

it seems that proc-macro used by a project panics, and those panics get printed to our stderr. I don't think we should do that, to not confuse them with real panics. Ideally, panic messge/trace should be stored as a String in macro exapnsion result