fix handling of aliases imports and exports

[crowlKats]

Import alias case:

a.ts

import { Data as Foo } from "./b.ts";
export interface Data {}
export function f(): Foo {}

b.ts

export interface Data {}

Export alias case:

a.ts

import { Data } from "./_util.ts";
export function f(): Data {

b.ts

export { type Data as Foo } from "./_util.ts";

_util.ts

export interface Data {}

cc @lucacasonato

[crowlKats]

Potentially related #427