Promote comby warnings and suggestions to alerts

Created by: rvantonder

Running comby on the command line will surface alerts for certain weird patterns (like when your pattern starts with :[x], which matches across newlines and thus matches a lot more things than intended. These warnings are currently suppressed.

I want to pass these warnings through to the web frontend, and some work is needed to filter certain warnings and nicely reformat others to be contextually useful.

Related: #9079 (closed) we should warn if a query is unbalanced.