Write "temporary AST" classes

[Lythenas]

To make using the Tree-Sitter-API in the Interpreter easier we need another layer of abstraction.

This abstraction should consist of "temporary" AST-Objects (similar to the once that already exist). It should not be necessary to copy the complete syntax tree from Tree-Sitter to this abstraction. Instead the objects should be created "on-the-fly" in the Interpreter and use the Tree-Sitter nodes internally.