Add explicit output parameters to spiking output ports #2237

Job	Run time
link_checker	8s
static_checks	37s
build_and_test_nest_desktop (master)	12m 27s
build_and_test_nest (v2.20.2)	29m 55s
build_and_test_nest_compartmental (master)	20m 18s
build_and_test_py_standalone	1m 46s
build_and_test_nest (v3.0)	23m 10s
build_and_test_nest (v3.8)	25m 29s
build_and_test_nest (master)	49m 2s
	2h 42m 52s

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