Merge branch 'develop-deprecate-uTypeType'. Close #484.

**Description**

The record field `uTypeType`, part of `Copilot.Core.Type.UType`, is
never really used within the module or in any other part of Copilot or,
as far as we know, by any user of Copilot. As a matter of fact, we
cannot use it to obtain the value inside the `UType` due to the
existential it encloses. It also makes the test report lower coverage
than they otherwise might, since the record access function is not used
by the tests.

This field is not necessary parts of the interface to use Copilot, and
not required by Copilot's requirements. Therefore, it would be suitable
to remove that definitions from the module.

As per our internal policy of waiting 3 versions from deprecation until
a public interface declaration can be removed, those definitions should
be deprecated.

**Type**

- Bug: unused code included in the implementation.

**Additional context**

None.

**Requester**

- Ivan Perez

**Method to check presence of bug**

The field is mentioned in the record definition, but making it a
non-record datatype, or not exporting that field in the module exports,
does not change the behavior and does not otherwise affect Copilot.
The code compiles without errors and behaves in the same way.

**Expected result**

The following elements are deprecated:
- `Copilot.Core.Type.UType.uTypeType`

The following Dockerfile tries to import and use uTypeType, printing
"Success" if the import is deprecated, and "Failure" otherwise:

```

ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update

RUN apt-get install --yes libz-dev
RUN apt-get install --yes git

RUN apt-get install --yes wget
RUN mkdir -p $HOME/.ghcup/bin
RUN wget https://downloads.haskell.org/~ghcup/0.1.19.2/x86_64-linux-ghcup-0.1.19.2 -O $HOME/.ghcup/bin/ghcup

RUN chmod a+x $HOME/.ghcup/bin/ghcup
ENV PATH=$PATH:/root/.ghcup/bin/
ENV PATH=$PATH:/root/.cabal/bin/
RUN apt-get install --yes curl
RUN apt-get install --yes gcc g++ make libgmp3-dev
RUN apt-get install --yes pkg-config

SHELL ["/bin/bash", "-c"]

RUN ghcup install ghc 9.8.2
RUN ghcup install cabal 3.2
RUN ghcup set ghc 9.8.2
RUN cabal update

SHELL ["/bin/bash", "-c"]
CMD git clone $REPO && cd $NAME && git checkout $COMMIT && cd .. \
  && cabal v1-sandbox init \
  && cabal v1-install $NAME/copilot-core/ \
  && ! cabal v1-exec -- runhaskell -XGADTs -Wall -Werror <<< 'import Copilot.Core.Type(UType(UType, uTypeType), Type(Int8)); main :: IO (); main = case UType Int8 of; (UType { uTypeType = Int8}) -> putStrLn "Failure"' \
  && echo "Success"
```

Command (substitute variables based on new path after merge):
```
$ docker run -e "REPO=https://github.com/Copilot-Language/copilot" -e "NAME=copilot" -e "COMMIT=<HASH>" -it copilot-verify-484
```

**Solution implemented**

Deprecate `Copilot.Core.Type.UType.uTypeType`.

**Further notes**

None.

Author: ivanperez-keera

copilot-core/CHANGELOG

@@ -1,6 +1,7 @@
-2024-10-19
+2024-10-28
         * Add Haddocks for updateField. (#525)
         * Standardize changelog format. (#550)
+        * Deprecate Copilot.Core.Type.UType.uTypeType. (#484)
 
 2024-09-07
         * Version bump (4.0). (#532)

copilot-core/src/Copilot/Core/Type.hs

@@ -268,6 +268,7 @@ instance (Typeable t, Typed t, KnownNat n) => Typed (Array n t) where
 
 -- | A untyped type (no phantom type).
 data UType = forall a . Typeable a => UType { uTypeType :: Type a }
+{-# DEPRECATED uTypeType "This field is deprecated in Copilot 4.1. Use pattern matching instead." #-}
 
 instance Eq UType where
   UType ty1 == UType ty2 = typeRep ty1 == typeRep ty2