Support as "PyAlias" in wrap_error

[jselig-rigetti]

Since capitalization style between initialisms differs between python (prefer QCSError), and rust (prefer QcsError) it would be nice to have a similar pattern to py_wrap_type to make an alias:

use rigetti_pyo3::{py_wrap_error, wrap_error, create_init_submodule};
use pyo3::exceptions::{PyRuntimeError};

wrap_error!(
    ClientError(some_other_mod::ClientError) as "QCSClientError" // <-- feels most similar to other patterns
);

py_wrap_error!(
    this_mod,
    ClientError,
    QcsClientError, // <-- in its current state, the internal `pyo3::crate_exception!` annotates this with
                    // `#[allow(non_camel_case_types)]` so it is acceptable to use `QCSClientError` here
                    // without any changes.
    PyRuntimeError,
    // <-- the internal `pyo3::create_exception!` macro takes an optional `doc` parameter
    // that we aren't using, some potential re-use there. 
);

create_init_submodule! {
    errors: [QcsClientError], // <-- calls `std::stringify!(QcsClientError)` so would need to be changed
}