Support for SMTPat on fields of an inductive

It would be nice to be able to do:

```
typeclass c {
lemma_foo: ... [ SMTPat ... ];
}
```

and be able to enjoy the pattern:

```
let f [| c |] =
// pattern in local scope
```

or, if not supported, at least warn about it. Santiago seconded this proposal.

Thanks,

Jonathan

Start by tracing how SMTPat annotations on typeclass lemmas and patterns over inductive fields are handled. Compare the requested examples with the current behavior, then determine whether support can be added or a warning should be emitted for the unsupported form.

Written by the indexing model from the issue text.