feat: allow model arguments to be registered outside #8519

Job	Run time
Test Python (1, 3.8)	25m 1s
Test Python (1, 3.11)	24m 24s
Test Python (2, 3.8)	23m 54s
Test Python (2, 3.11)	22m 57s
Test Python (3, 3.8)	24m 37s
Test Python (3, 3.11)	23m 3s
Test Python (4, 3.8)	24m 15s
Test Python (4, 3.11)	23m 43s
Test Python (5, 3.8)	24m 56s
Test Python (5, 3.11)	24m 27s
Test Python (6, 3.8)	25m 5s
Test Python (6, 3.11)	23m 36s
Combine and update integration test durations (3.8)	53s
Combine and update integration test durations (3.11)	47s
Pass testing Python	3s
	4h 51m 41s

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