[WIP] Allow named layers and some Misc Fixes

[avik-pal]

Example

julia> c = Chain(feature_extractor=Chain(Dense(2, 3, relu), BatchNorm(3)),
                 classifier=Chain(Dense(3, 2)))
Chain(
    feature_extractor = Chain(
        layer_1 = Dense(2 => 3, relu),  # 9 parameters
        layer_2 = BatchNorm(3),         # 6 parameters, plus 7
    ),
    classifier = Dense(3 => 2),         # 8 parameters
)         # Total: 23 parameters,
          #        plus 7 states, summarysize 48 bytes.

[codecov]

Codecov Report

Merging #44 (78eb5fb) into main (7e8ce8e) will increase coverage by 0.05%.
The diff coverage is 44.04%.

@@            Coverage Diff             @@
##             main      #44      +/-   ##
==========================================
+ Coverage   45.07%   45.13%   +0.05%     
==========================================
  Files          13       13              
  Lines         945      955      +10     
==========================================
+ Hits          426      431       +5     
- Misses        519      524       +5     

Impacted Files	Coverage Δ
src/Lux.jl	100.00% <ø> (ø)
src/adapt.jl	0.00% <0.00%> (ø)
src/layers/display.jl	0.00% <0.00%> (ø)
src/layers/normalize.jl	34.28% <0.00%> (ø)
src/utils.jl	46.98% <20.00%> (ø)
src/layers/basic.jl	38.65% <27.58%> (-0.41%)	⬇️
src/core.jl	56.52% <41.66%> (-3.95%)	⬇️
src/nnlib.jl	61.68% <45.45%> (ø)
src/autodiff.jl	48.00% <83.33%> (+5.77%)	⬆️
src/layers/conv.jl	47.11% <100.00%> (ø)
... and 2 more

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[avik-pal]

Closing this since, most features have been pulled into different PRs (already in main). We still need to work on named layers for container types.