[AArch64]Combine BFXIL to ORR with right shift for ISD::OR instruction selection

- This extends the existing helper function 'isWorthFoldingIntoOrrWithLeftShift' into
  'isWorthFoldingIntoOrrWithShift', and encode right-shift imm (the
  encoding of left-shift imm is no-op).

Reviewed By: dmgreen

Differential Revision: https://reviews.llvm.org/D137465