Fixup: rich compiler output in warnings

[ferd]

I hadn't seen this because all my projects use warnings_as_errors, but the warnings were never properly wired up.

This patch fixes that by adding the proper callbacks and invoking them from the 3 erlang-related compilers we support.

Sample run:

→ rebar3 as test compile
===> Verifying dependencies...
===> Analyzing applications...
===> Compiling revault
===> Compiling maestro
    ┌─ apps/revault/test/id_shim.erl:
    │
 23 │  id_ask(From, To) ->
    │               ╰── Warning: variable 'To' is unused


===> Analyzing applications...
===> Compiling extra_test

This might look a bit like an error but yeah, not a good way to bypass that for now without further re-structuring of the code.