feat: update ConvMixer to support reactant #3877

Job	Run time
downgrade	4m 59s
test (1.10, ubuntu-latest, core_layers)	19m 39s
test (1.10, ubuntu-latest, normalize_layers)	20m 2s
test (1.10, ubuntu-latest, recurrent_layers)	28m 31s
test (1.10, ubuntu-latest, autodiff)	48m 23s
test (1.10, ubuntu-latest, misc)	28m 18s
test (1.10, ubuntu-latest, reactant)	4m 19s
test (1, ubuntu-latest, core_layers)	23m 57s
test (1, ubuntu-latest, normalize_layers)	24m 25s
test (1, ubuntu-latest, recurrent_layers)	36m 14s
test (1, ubuntu-latest, autodiff)	34m 35s
test (1, ubuntu-latest, misc)	32m 29s
test (1, ubuntu-latest, reactant)	6m 45s
test (1, macos-latest, all)	7m 12s
test (1, windows-latest, all)	1h 36m 46s
	6h 56m 34s

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