i965/nir/vec4: Implement bit operations
i965/nir/vec4: Implement bit operations

Same implementation than the IR case.

Adds NIR ALU operations:
   * nir_op_bitfield_reverse
   * nir_op_bit_count
   * nir_op_ufind_msb
   * nir_op_ifind_msb
   * nir_op_find_lsb
   * nir_op_ubitfield_extract
   * nir_op_ibitfield_extract
   * nir_op_bfm
   * nir_op_bfi
   * nir_op_bitfield_insert

Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler