[ADP-3169] Implement "physical identities" for modules

[HeinrichApfelmus]

This pull request implements

• "physical" identities for modules, and
• provenance information about the module in which a TypName is defined.

This is necessary in order to support multiple inclusions of the same module with different instances for imports.

As a first, somewhat simplistic use case, we add an assertion for equality of modules in the package description:

package Test where

module X from "X.fine";
module Xoops renaming X from "X.fine";
assert X == Xoops;

Issue number

ADP-3169