Add broadcast support for python binding packetflow op

[fifield]

This adds support for multiple destinations to the mlir-aie python binding for packetflow op.

example from the unit test:

    t0 = tile(col=1, row=3)
    t1 = tile(col=2, row=4)
    packetflow(
        pkt_id=0x10,
        source=t0,
        source_port=WireBundle.DMA,
        source_channel=0,
        dests=[
            {"dest": t0, "port": WireBundle.DMA, "channel": 1},
            {"dest": t1, "port": WireBundle.DMA, "channel": 1},
        ],
        keep_pkt_header=True,
    )

produces,

  %tile_1_3 = aie.tile(1, 3)
  %tile_2_4 = aie.tile(2, 4)
  aie.packet_flow(16) {
    aie.packet_source<%tile_1_3, DMA : 0>
    aie.packet_dest<%tile_1_3, DMA : 1>
    aie.packet_dest<%tile_2_4, DMA : 1>
  } {keep_pkt_header = true}

The change is to replace the destination arguments with a list of dicts with one dict per destination:
replace,
packetflow(..., dest=tile, dest_port=port, dest_channel=channel, ...)
with,
packetflow(..., dests=[{dest=..., port=..., channel=...}, ...], ...)