MDF: Mechanism: fix multiple input ports with multiple afferents #10217

Job	Run time
build (3.8, x64, ubuntu)	1h 32m 40s
build (3.8, x64, windows)	1h 33m 57s
build (3.11, x64, ubuntu)	1h 18m 10s
build (3.11, x64, macos)	29m 59s
build (3.11, x64, windows)	1h 35m 15s
build (3.12, x64, ubuntu)	1h 18m 56s
build (3.12, x64, macos)	36m 32s
build (3.12, x64, windows)	1h 31m 51s
build (3.9, macos, --cov=psyneulink)	48m 37s
build (3.9, ubuntu, --forked -m "not llvm")	39m 20s
build (3.9, x86, windows)	1h 36m 34s
build (3.10, ubuntu, --fp-precision=fp32)	1h 18m 29s
build (3.10, macos, -m benchmark --benchmark-enable --benchmark-only --benchmark-min-rounds=2 --b...	25m 12s
build (3.8, macos, min)	37m 4s
	15h 22m 36s

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