Add flexible metadata system

[tobiasploetz]

Summary

This PR implements a flexible metadata system for annotating BayBE objects with a description, unit, and other information. So far integrated into Parameter only.

Usage Example

from baybe.parameters import NumericalDiscreteParameter, ParameterMetadata
from baybe.utils.metadata import to_metadata

# Using dict
# (Gets automatically converted and entries are separated into known and misc fields)
dct = {"description": "Reaction temperature", "unit": "°C", "custom_field": "value"}
param = NumericalDiscreteParameter(
    name="temperature", values=[90, 105, 120], metadata=dct
)

# Using Metadata class directly
meta = ParameterMetadata(
    description="Reaction temperature", unit="°C", misc={"custom_field": "value"}
)
param = NumericalDiscreteParameter(
    name="temperature", values=[90, 105, 120], metadata=meta
)

assert meta == to_metadata(dct, ParameterMetadata) == ParameterMetadata.from_dict(dct)

# Accessing metadata
print(param.description)  # "Reaction temperature"
print(param.unit)  # "°C"

[AdrianSosic]

Hey @dasmy. This PR is basically ready for merge but since you also raised that same request, I wanted to hear your thoughts on whether it aligns with your expectations. Anything missing? Regarding the idea to generalize this to all classes --> we can follow up on this in a separate PR. This one here is just to provide the basic skeleton and necessary machinery for serialization so that @tobiasploetz can continue integrating the LLM recommender. But feel free to share any thoughts that come to your mind 🧠

[dasmy]

Thanks for setting this up. This is exactly what I had in mind for #580 .
As noted there, I would love to see this for essentially all serializable objects: Targets will have similar needs like Parameters; Constraints, etc. will likely only need some kind of description support, but who knows what others need.
So definitely green light from my perspective as this is the right step into the right direction. - Will use it ASAP in MTPilot as well ;-)

[AdrianSosic]

Alright, waiting for @Scienfitz's opinion and then we can merge. One thing to discuss: as mentioned in one of the comments, I see the current Metadata class directly applicable to Parameter and Target, and I think they will always share the same set of fields. However, since we probably also want to extend this to Objective and other objects, the unit field is already too specific to have it in the base class. So perhaps it makes sense to split the class into an actual base class that only contains description and unit, and introduce a subclass that is then used for Parameter and Target? Not sure what would be a good name, but basically it would reflect the metadata for a sort of "basic univariate measureable component". Can discuss in the dev meeting

[AVHopp]

LGTM, thanks for the work :)

[AVHopp]

@AdrianSosic could you please add ".env" as another exception as well? Did some cleaning and setup of my local IDE and that would be super helpful :)