Fix package module resolution in inline imports

We were still passing `ModuleIds` from `load` to `can`, but now
that imports can appear in any scope, we don't know which package
an unqualified module name belongs to from the top level.

We now pass `PackageModuleIds` instead  and keep a Map of `ModuleName` to
`ModuleId` in `Scope`.

This also allow us to import multiple modules with the same name from different
packages as long as a unique alias is provided.

crates/compiler/load_internal/src/module.rs

@@ -198,6 +198,7 @@ pub struct ParsedModule<'a> {
     pub packages: MutMap<&'a str, PackageName<'a>>,
     pub initial_scope: MutMap<Ident, (Symbol, Region)>,
     pub exposes: Vec<Symbol>,
+    pub opt_shorthand: Option<&'a str>,
 }
 
 #[derive(Debug)]