Fixes to type stability of Zygote

[avik-pal]

• [x] Common Layers & their type stability with Zygote
  • [x] Dense
    • [x] CPU
    • [x] CUDA
  • [x] Chain
    • [x] CPU
    • [x] CUDA
  • [x] BatchNorm
    • [x] CPU
    • [x] CUDA
  • [x] GroupNorm
    • [x] CPU
    • [x] CUDA
  • [x] InstanceNorm
    • [x] CPU
    • [x] CUDA
  • [x] Conv
    • [x] CPU
    • [x] CUDA
  • [x] LayerNorm
    • [x] CPU
    • [x] CUDA
  • [x] Dropout
    • [x] CPU
    • [x] CUDA
  • [x] Parallel
    • [x] CPU
    • [x] CUDA
  • [x] Branch Layer
    • [x] CPU
    • [x] CUDA
  • [x] AdaptiveMaxPooling
    • [x] CPU
    • [x] CUDA
  • [x] AdaptiveMeanPooling
    • [x] CPU
    • [x] CUDA
  • [x] MaxPooling
    • [x] CPU
    • [x] CUDA
  • [x] MeanPooling
    • [x] CPU
    • [x] CUDA
  • [x] GlobalMaxPooling
    • [x] CPU
    • [x] CUDA
  • [x] GlobalMeanPooling
    • [x] CPU
    • [x] CUDA
  • [x] Repeated Layer
    • [x] CPU
    • [x] CUDA
  • [x] Pairwise Fusion
    • [x] CPU
    • [x] CUDA
  • [x] Alpha Dropout
    • [x] CPU
    • [x] CUDA
• [x] Add Tests
• [x] Needs https://github.com/LuxDL/LuxLib.jl/pull/67

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.56%. Comparing base (b6cbee3) to head (8941c89).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #635 +/- ## ========================================== + Coverage 87.51% 87.56% +0.05% ========================================== Files 47 47 Lines 2339 2341 +2 ========================================== + Hits 2047 2050 +3 + Misses 292 291 -1 ```

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