[SMT] Implicit overflow when parsing `!smt.bv` type?

Nobody has claimed this yet.

When providing the following as input to `circt-opt`
```
hw.module @ImplicitOverflow() {
%0 = smt.bv.constant #smt.bv<1> : !smt.bv<18446744073709551615>
}
```
it outputs
```
hw.module @ImplicitOverflow() {
%c1_bv4294967295 = smt.bv.constant #smt.bv<1> : !smt.bv<4294967295>
hw.output
}
```

Using `!smt.bv<18446744073709551616>` as input expectedly triggers an error that the integer is too large.
Seems like we store it in some 32 bit integer at some point?

Reproduce the issue with the provided input using circt-opt, then trace parsing and storage of the !smt.bv width. Ensure 18446744073709551615 is preserved rather than truncated, while 18446744073709551616 still reports that the integer is too large.

Written by the indexing model from the issue text.