fix: add missing ap_axi_sdata.h and sort includes

[taraxacum45e9a]

Building the dcmac_emu target for examples/06_dcmac failed because hls::axis, used in the generated testbench, is declared in <ap_axi_sdata.h>, which was not included in the template.

The generated prototypes are:

void traffic_producer(hls::stream<hls::axis<ap_uint<512>, 1, 1, 3, '8', false>>& axis_out, ap_uint<32> flits, ap_uint<3> dest);
void traffic_consumer(hls::stream<hls::axis<ap_uint<512>, 1, 1, 3, '8', false>>& axis_in, ap_uint<32>& rx_flits);

Changes

• Add <ap_axi_sdata.h> to provide the hls::axis type definition.
• Sort includes into two groups — standard library headers first, then third-party/HLS headers — each group ordered alphabetically.