[ refactor ] Refactor and optimize CaseBuilder (#16)

* [ refactor ] Replace `rev` with `reverse` and make `LengthMatch` arguments erased

* [ refactor ] Move `embed'` definition into `FreelyEmbeddable` implementation

* [ refactor ] Optimize `mkPatClause.mkNames` in `CaseBuilder`

* [ refactor ] Swap parameters of `NamedPats`

* [ refactor ] Remove `snoc` for `NamedPats`

* [ refactor ] Use `List` for forward order in `CaseBuilder.idr`

* [ refactor ] Swap the arguments of `PatClause`, `Group` and `ScoredPats` like `NamedPats`

* [ refactor ] Merge simillar cases in `nextNames'` and `mkNames`

* [ cleanup ] Remove redudant functions

Cherry-picked from GulinSS#16
Fully authored by Viktor Yudov <[email protected]>

Co-authored-by: Viktor Yudov <[email protected]>

Author: GulinSS