Proposed change to waveder

[jmmshn]

https://github.com/materialsproject/pymatgen/blob/722ea4648bbcd9e792991e51365fed5b78eba3f4/pymatgen/io/vasp/outputs.py#L5509

Currently, there are two Waveder objects basically accomplish the same thing be just have two different constructor methods. They also cannot be serialized since their __init__ requires the filename. Proposed change:

• Combine the two objects into one Waveder dataclass object with the cder data.
• Change the two different constructors from_waveder and from_wavederf.

Let me know if this messes with anyone's stuff (especially the original author @migueldiascosta) and I will PR.

Best

[shyuep]

I support this proposal. Pls implement and submit a PR. Thanks.