[Haskell] Fix data constructor definitions (#3241)

This PR addresses some points from #3227.

1. It reorganizes prelude type/constant scopes, so `Just`, `Nothing`,
    `Left` and `Right` are highlighted consistently.
2. It scopes data constructors in data declarations `entity.name.constant`.
3. As a preparation for 2.) the strategy to handle `[context] =>` 
   expresssions in class/data/newtype/type declarations had to be
   changed a bit to (more) reliably. It is mainly required to detect
   the beginning of data constructor expressions (`= Constr`),
   but also helps with some edge cases in the other declarations.

Note: This PR does not scope data types and data constructors
differently in normal statements/expressions as no reliable strategy
hasn't been found to do so.

* [Haskell] Reorganize and add prelude type and data constructors

According to Haskell's wording ...

- type constructors are scoped `support.type`, `storage.type`
  Type constructors without parameters are called "type".

- data constructors are scoped `support.constant`, `constant.other`
  Data constructors without parameters are called "constant".

  Data constructors denote first class values. As such they can be
  assigned to variables etc.

See: https://wiki.haskell.org/Constructor

* [Haskell] Reorganize class identifier contexts

Merge class and type contexts as it is not possible to reliably
distinguish both in all situations anyway. The common scope
`storage.type` ensures same highlighting under all circumstances.

* [Haskell] Improve declaration context

This commit...

1. adds some infrastructure to make sure to correctly match 
   `[context] =>` patterns in class/instance/data/type/newtype
   declarations. It's required to reliably match the beginning of
   data constructors.

2. removes `entity.name.class` scoping from instance declarations as
   this was semantically wrong.

* [Haskell] Improve deriving expression

This commit limits fully qualified data type matching to 1 after
`deriving` keywords, in case they are not surrounded by parens.

More reliably pop as soon as possible.

* [Haskell] Fix data constructor definitions

This commit adds data constructor expressions in order to 
1. scope constructors `entity.name.constructor` in declarations.
2. add declared constructor names to Symbol List.
3. enable "Goto Definition"

It should improve readability of constructor expressions as the
declared constructor may be tinted differently then the following types
which define its signature.