[enhancement] parametric support for type aliases

### What's hard to do? (limit 100 words)

Currently you can really do things like:

```
type Index = uN[std::clog2(u32) + u32:1];
```
or
```
struct SomeDataChunk {
type Index = uN[std::clog2(u32) + u32:1],
data: u32[N],
index_start: Index,
index_end: Index,
}
```

### Current best alternative workaround (limit 100 words)

Hardcode the type or duplicate the type expression everywhere it's being used.

### Your view of the "best case XLS enhancement" (limit 100 words)

Add support for arbitrary parameterized type alias in all context:
- struct body
- proc body
- parametric definition