Fix: Popping a parent route should also pop all child routes

[zssnyder]

Description

This PR is intended to fix issue #960. Additional checks were added when popping from the navigation stack to prevent leaving orphaned navigation routes or modules. These changes ensure all child routes are removed from navigation history and that the enclosing module will be disposed if no other routes from that module exist on the stack.

Checklist

• [x] The title of my PR starts with a [Conventional Commit] prefix (fix:, feat:, docs: etc).
• [x] I have read the [Contributor Guide] and followed the process outlined for submitting PRs.
• [x] I have updated/added tests for ALL new/updated/fixed functionality.
• [ ] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [ ] I have updated/added relevant examples in examples.

Breaking Change

• [ ] Yes, this is a breaking change.
• [x] No, this is not a breaking change.

Related Issues

Fixes #960