Draft: aco: Merge "break" and "continue" block if "break" falls through to "continue".

This would be a lot more effective if NIR wouldn't prefer to increment for-loop counters in the continue block.

Foz-DB Navi21:
Totals from 317 (0.23% of 134913) affected shaders:
Instrs: 406673 -> 405245 (-0.35%)
CodeSize: 2202372 -> 2196660 (-0.26%)
Latency: 8290074 -> 8288367 (-0.02%); split: -0.03%, +0.01%
InvThroughput: 8426508 -> 8428773 (+0.03%); split: -0.00%, +0.03%
Copies: 38319 -> 37605 (-1.86%)
Branches: 11439 -> 10725 (-6.24%)