Add `coconut -m` support

Should look up the module for import, compile it, then run `python -m` to execute it. Should be incompatible with `-r` or `-i`. Should also work for `coconut-run` and should immediately go to `--argv` after `-m module` when using `coconut-run -m`.

Start by tracing argument parsing and execution for the `coconut` and `coconut-run` commands, especially handling of `-m`, `-r`, `-i`, and `--argv`. Done means `-m module` looks up and compiles the module before running it with `python -m`, rejects incompatible modes, and passes directly to `--argv` for `coconut-run`.

Written by the indexing model from the issue text.