We cannot handle them normally since we need text between parenthesis to
be a valid expression. As a workaround, we now push an artificial value
to stack to act as an argument (it'll be later removed during function
call canonicalization).
In a bunch of cases, this actually ends up simplifying the code as
to_number will handle something such as:
```
Optional<I> opt;
if constexpr (IsSigned<I>)
opt = view.to_int<I>();
else
opt = view.to_uint<I>();
```
For us.
The main goal here however is to have a single generic number conversion
API between all of the String classes.
