Refactor `ObjectList` implementation

Problem

The current Objectlist (the object that wraps a collection of API results, f.i. "get payments") is a messy class.

• It supports some methods that make it behave as a list, but also some dictionary-like behaviors.
• Iterating over paginated results is something that a developer must do in code, it is not provided by the client.
• It is initialized using a complex data structure (a full API response) which makes the code handling this data hard to read

Improvements

• Consume only the list data from the API response (Also see the TODO in code: https://github.com/mollie/mollie-api-python/blob/5b63136b4a7f5543ded9fb4141b7b6feaaada7a1/mollie/api/objects/list.py#L17-L19)
• Automatic iteration over paginated API results
• Expose only list behavior

In #285 a POC is available. This should be properly integrated and tested.

Start with mollie/api/objects/list.py, especially the TODO linked in the issue, and review the proof of concept in #285. Trace the current API response handling and pagination behavior, then verify that the integrated object consumes list data, iterates paginated results automatically, exposes only list behavior, and has tests for these changes.