revamp Parameterized typeclass and add misc additional functionality

[tscholak]

I've put everything non-experimental in #447 in this PR because these things are ready to be merged and make live easier for everyone.

The biggest change is the new Torch.Typed.Parameter.Parameterized type class:

class
  Parameterized (f :: Type)
  where
  type Parameters f :: [Type]
  type Parameters f = GParameters (Rep f)
  flattenParameters :: f -> HList (Parameters f)
  default flattenParameters ::
    (Generic f, GParameterized (Rep f), Parameters f ~ GParameters (Rep f)) =>
    f ->
    HList (Parameters f)
  flattenParameters f = gFlattenParameters (from f)
  replaceParameters :: f -> HList (Parameters f) -> f
  default replaceParameters ::
    (Generic f, GParameterized (Rep f), Parameters f ~ GParameters (Rep f)) =>
    f ->
    HList (Parameters f) ->
    f
  replaceParameters f as = to (gReplaceParameters (from f) as)

The old one was:

class
  Parameterized
    (f :: Type)
    (as :: [Type])
    | f -> as where
  flattenParameters :: f -> HList as
  replaceParameters :: f -> HList as -> f

The new one doesn't have functional dependencies, has one type parameter less, uses default signatures to delegate implementations to generics, and provides the Parameters type family that computes the list of parameters for a given model ADT.

You can use DeriveAnyClass with the deriving syntax now to ask for a Parameterized instance for any model ADT that has a Generic instance:

{-# LANGUAGE DeriveAnyClass #-}

...

data MyModel = MyModel (Generic, Parameterized)

If this compiles, you can use Parameters MyModel to ask GHC for the list of parameters of your model. Within ghci, this would be:

> :kind! Parameters MyModel
'[]

or something to that effect. (This example has no parameters, therefore the empty type-level list.)

[tscholak]

hmm, doctests are failing with stack.

could be this issue:

/home/runner/work/hasktorch/hasktorch/hasktorch/src/Torch/Typed/NN/Transformer.hs:177:10: error:
    Illegal `..' notation for constructor ‘MultiheadAttentionSpec’
      The constructor has no labelled fields
    |
177 |   sample MultiheadAttentionSpec {..} =
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^

[junjihashimoto]

Very nice. Thank you very much.

There are newtype Parameter and type class Parameters, one is like a value, and the other is a function, so I feel that we need to be careful when coding. Both of them are type level, so they start with capital letters.
I feel good as it is.