Add support for ReactPy v2.x

[shawncrawley]

Description

This is my attempt to update reactpy-router to work with the ReactPy v2.0 pre-release package.

Checklist

Please update this checklist as you complete each item:

• Tests have been developed for bug fixes or new functionality.
• The changelog has been updated, if necessary.
• Documentation has been updated, if necessary.
• GitHub Issues closed by this PR have been linked.

_{By submitting this pull request I agree that all contributions comply with this project's open source license(s).}

[shawncrawley]

When I run the test suite locally, I still have one test failing that I couldn't figure out how to fix: test_simple_router. The failure is coming from code that was introduced years ago and hasn't changed since. It's this line here:

reactpy-router/tests/test_router.py

Line 52 in 898c8fd

f"#display-{display._next_view_id}", # type: ignore

It is failing with: AttributeError: 'DisplayFixture' object has no attribute '_next_view_id'

I used various AI searches and did a lot of digging to find out how that could have ever worked and thus hopefully discover the required refactor, but unfortunately my searching came up empty.

[Archmonger]

I've fixed all issues within this PR, and have reviewed the changes.

Approved.