feat: update ConvMixer to support reactant #3927

Job	Run time
downgrade	4m 57s
test (1.10, ubuntu-latest, core_layers)	19m 17s
test (1.10, ubuntu-latest, normalize_layers)	19m 55s
test (1.10, ubuntu-latest, recurrent_layers)	28m 34s
test (1.10, ubuntu-latest, autodiff)	47m 49s
test (1.10, ubuntu-latest, misc)	29m 40s
test (1.10, ubuntu-latest, reactant)	7m 53s
test (1, ubuntu-latest, core_layers)	24m 25s
test (1, ubuntu-latest, normalize_layers)	26m 16s
test (1, ubuntu-latest, recurrent_layers)	35m 12s
test (1, ubuntu-latest, autodiff)	34m 59s
test (1, ubuntu-latest, misc)	33m 30s
test (1, ubuntu-latest, reactant)	9m 30s
test (1, macos-latest, all)	5h 1m 45s
test (1, windows-latest, all)	1h 35m 4s
	11h 58m 46s

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