Add merged payload error bit support in design and in tb.

...2_unb2c_sdp_station_bf/tb_lofar2_unb2c_sdp_station_bf.vhd

...p_station_bf_ring/tb_lofar2_unb2c_sdp_station_bf_ring.vhd

...s/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_output.vhd