Add non-async variants for `BlackBoxUQ` and `LLMPanel` methods

[nobodyPerfecZ]

Is your feature request related to a problem? Please describe.
The current uqlm API only exposes asynchronous versions of the core methods inside of BlackBoxUQ and LLMPanel. This forces users to run everthing inside an event loop.

Describe the solution you'd like
Provide a non-async function of the necessary methods inside of BlackBoxUQ and LLMPanel so that users can choose between async and sync execution modes, similar to LangChain’s abatch/batch.