Unit test the rs1/rs2 bins cgs.

[jerralph]

These covergroups are one of the few that are not unit tested, and of course if it's not tested it has bugs. Issue 6333684 shows a bug in this where bins was used where ignore_bins was meant. I found it while looking at coverage reports.

[jerralph]

Fix for 6333684 was wrong and next attempt, 8d9a12b, looks good so far