Turn off virtualizer when running in test env (#5192)
* rough progress on making virtualized components non-reliant on clientHeight/Width mocks
* Update virtualizer to get proper mocked rect in test env
* update the remaining failing tests
* use mocks if provided
* fix clientwidth mock check
* skip problematic tests and show examples how we dont need the mocks
* ugh, figured out the react 16/17 crash
too many rows being rendered... not anything with the extra render cycles or broken virtualizer logic
* getting rid of todos and reseting tests
* adding a extra process env to make sure we always run with virtualizer enabled in CI
* vscode auto updates...
