[dv/clkmgr] Test different rst_io* and rst_root_io*

### Description

clkmgr has rst_io_ni, rst_io_div2_ni, and rst_io_div4_ni. Similarly it has three rst_root_io*. The testbench hooks them all to the same interface.

We should hook these to different interfaces and create simple tests that send different stimuli to each in order to verify they behave as expected.

This seems like a low priority test since the functional differences between them are pretty simple.