feat: update ConvMixer to support reactant

[avik-pal]

• Needs conv adjoints conv gradient is not implemented in EnzymeJAX EnzymeAD/Reactant.jl#214
• Needs reduce_window adjoint -- we could potentially work around this
• Incorrect gradients issue?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 76.31%. Comparing base (51c0e47) to head (fee949f).

Files with missing lines	Patch %	Lines
src/layers/pooling.jl	0.00%	4 Missing ⚠️
ext/LuxReactantExt/patches.jl	0.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (51c0e47) and HEAD (fee949f). Click for more details.

HEAD has 25 uploads less than BASE

Flag	BASE (51c0e47)	HEAD (fee949f)
	46	21

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1063      +/-   ##
==========================================
- Coverage   82.83%   76.31%   -6.53%     
==========================================
  Files         147      145       -2     
  Lines        6072     6049      -23     
==========================================
- Hits         5030     4616     -414     
- Misses       1042     1433     +391     

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[github-actions]

Benchmark Results (ASV)

	main	a7fb9c9...	main/a7fb9c921f0b31...
basics/overhead	0.122 ± 0.0014 μs	0.135 ± 0.005 μs	0.909
time_to_load	0.898 ± 0.0037 s	0.904 ± 0.0085 s	0.994

Benchmark Plots

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Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).

[avik-pal]

Not completely functional yet "error: expects input feature dimension (256) / feature_group_count = kernel input feature dimension (256). Got feature_group_count = 256."

xref: EnzymeAD/Reactant.jl#331

[avik-pal]

Unfortunately there is a strong discrepancy in the gradients between Zygote and Reactant. Need to debug