[RISCV] Implement isMaskAndCmp0FoldingBeneficial hook

This hook is currently only used by CodeGenPrepare, which will sink *and
duplicate* an 'and' into a block that has an 'icmp 0' user of it if the
hook returns true.

This hook is less useful for RISC-V than for targets like AArch64 that
have a TBZ (test bit and branch if zero instruction), but may still be
profitable if Zbs is available and a BEXTI can be selected.

Conservatively, we return false even if Zbs is enabled for any masks
that fit in the ANDI immediate because it's possible the only use is a
branch on the result, and ANDI+BNEZ => BEXTI+BNEZ isn't a profitable
transformation.

Differential Revision: https://reviews.llvm.org/D131492