MDF: Mechanism: fix multiple input ports with multiple afferents #10212

Job	Run time
build (3.8, x64, ubuntu)	1h 31m 3s
build (3.8, x64, windows)	1h 33m 22s
build (3.11, x64, ubuntu)	1h 17m 54s
build (3.11, x64, macos)	38m 45s
build (3.11, x64, windows)	1h 35m 6s
build (3.12, x64, ubuntu)	1h 19m 42s
build (3.12, x64, macos)	33m 6s
build (3.12, x64, windows)	1h 34m 33s
build (3.9, macos, --cov=psyneulink)	1h 3m 20s
build (3.9, ubuntu, --forked -m "not llvm")	40m 40s
build (3.9, x86, windows)	1h 38m 37s
build (3.10, ubuntu, --fp-precision=fp32)	1h 17m 19s
build (3.10, macos, -m benchmark --benchmark-enable --benchmark-only --benchmark-min-rounds=2 --b...	24m 57s
build (3.8, macos, min)	37m 15s
	15h 45m 39s

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