Copy the `testbed/ui` over to `bevy_examples` with a modified copy of the example runner executing off of `bevy_examples`

This sub issue is primarily to ensure that the example runner can be successfully updated to reference testbeds in the `bevy_examples` crate.

This should also ensure that https://github.com/bevyengine/bevy-example-runner has everything it needs to run things in `bevy_examples`

Start by inspecting the existing testbed/ui and the bevy_examples crate, then trace how the example runner references testbeds. Check the bevy-example-runner repository for the runner changes needed to execute examples from bevy_examples. Done means the copied testbed runs through the modified runner and the runner has everything required to use bevy_examples.

Written by the indexing model from the issue text.