Stress test parameter group options

[ConnorStoneAstro]

We need to write a more complete unit test suite for parameter groups under a number of edge cases. For example, we should test parameter groups in hierarchical models (both at the top level and within the hierarchy). It would also be good to test groups with varying batch dimensions, the batch dims of two separate groups should be independent. Parameter groups should be tested against basically all other features of caskade to make sure everything runs smoothly.