HMR End to end tests

[ItsMeBrianD]

In #3041 a few HMR tests were removed because of a Vite oddity causing full page reloads.

If a page has been visited previously, then changes made to it are eligible for HMR - however if a page has not been visited since the dev server started, then changes will cause a full page reload.

The tests for adding / removing pages were inaccurate because of this ( the test run shares a single dev server ), and full page reloads were occurring when running the tests in isolation. Because this is a minor DX issue, we've opted to remove those tests until more time can be allocated to fixing this behavior.