Fix adding duplicate fields when they are coming from an extended class

[spinillos]

Fixes: https://github.com/grafana/schematization-and-as-code-project/issues/64

The main issue was the way that we are unifying the values in nolit. Executing Unify itself, it adds extra nested levels for every new value. It only "detects" the nested value as an extended interface and its why it only works with the last value defined.

For any reason, use an empty Value to generate the tree does the trick 🤷🏻‍♀️.

More "visual" example should be:

A: {
  B
  C
  D
}

B: {
 b: string
}

C: {
  c: string
}

D: {
  d: string
}

It was generating:

:
(struct)

:
[&]  (struct)
├── (struct)
└── (struct)

:
[&]  _|_
├── [&]  (struct)
│   ├── (struct)
│   └── (struct)
└── (struct)

:
[&]  _|_
├── [&]  (struct)
│   ├── [&]  (struct)
│   │   ├── (struct)
│   │   └── (struct)
│   └── (struct)
└── (struct)

Now:

:
(struct)

:
[&]  (struct)
├── (struct)
└── [&]  (struct)
    ├── (struct)
    └── (struct)

:
[&]  (struct)
├── (struct)
└── [&]  (struct)
    ├── [&]  (struct)
    │   ├── (struct)
    │   └── [&]  (struct)
    │       ├── (struct)
    │       └── (struct)
    └── (struct)

:
[&]  (struct)
├── (struct)
└── [&]  (struct)
    ├── [&]  (struct)
    │   ├── (struct)
    │   └── [&]  (struct)
    │       ├── [&]  (struct)
    │       │   ├── (struct)
    │       │   └── [&]  (struct)
    │       │       ├── (struct)
    │       │       └── (struct)
    │       └── (struct)
    └── (struct)

So BottomKind disappears.

[sdboyer]

i'm not sure i quite grok why this fixed it, but clearly it did :)