aco,aco/tests: do not clause NSA instructions and test form_hard_clauses()

According to LLVM, creating hard clauses with NSA instructions has "unpredictable results on GFX10.1".

https://reviews.llvm.org/D102211

fossil-db (Navi10):

Totals from 26690 (17.81% of 149839) affected shaders:
CodeSize: 167935160 -> 167706280 (-0.14%); split: -0.14%, +0.00%
Instrs: 31801427 -> 31744142 (-0.18%); split: -0.18%, +0.00%
Latency: 732672435 -> 732622463 (-0.01%)
InvThroughput: 163361435 -> 163357838 (-0.00%); split: -0.00%, +0.00%
VClause: 546131 -> 546903 (+0.14%); split: -0.00%, +0.14%