lib: Introduce a for_each_connected_output() macro
lib: Introduce a for_each_connected_output() macro

So we can easily cycle through them in tests without knowing too many
internal details about how igt_display_t organize its data.

Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

dlespiau/checkmate-test-igt,tiagovignatti/intel-gpu-tools,rib/intel-gpu-tools,rib/intel-gpu-tools,dlespiau/checkmate-test-igt,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,erikarn/intel-gpu-tools,erikarn/intel-gpu-tools,rib/intel-gpu-tools,chenxianqin/intel-gpu-tools,rib/intel-gpu-tools,erikarn/intel-gpu-tools,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,yipdw/intel-gpu-tools,yipdw/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,yipdw/intel-gpu-tools,tiagovignatti/intel-gpu-tools,yipdw/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools