Replace `get_revoke_commit_msgs` macro with a function

Replace `get_revoke_commit_msgs` macro with a function

The `get_revoke_commit_msgs!()` macro has no reason to be a macro
so here we move its logic to a function and leave the macro in
place to avoid touching every line of code in the tests.

This reduces the `--profile=test --lib` `Zpretty=expanded` code
size from 324,763 LoC to 322,183 LoC.