[RISCV] Add more tests for rotate idioms. Add more RUN lines. NFC

We were only testing rotate idioms on rv32i. DAGCombiner won't
form ISD::ROTL/ROTR unless those operations are Legal or Custom.
They aren't for rv32 so we were only testing shift lowering.

This commit adds i64 idioms and the idioms that mask the shift
amount to avoid UB for a rotate of 0. I've added riscv64 and Zbb
RUN lines to show that we do match rotate for XLen types when
available. We currently miss i32 on rv64izbb.