Bug: Encoder kwargs strangely sensitive to format

[odunbar]

Issue

I have noticed that if one supplies

emulator = Emulator(mlt, train_pairs; encoder_schedule = encoder_schedule, encoder_kwargs = (; obs_noise_cov = Γ))

Then one has success, while

emulator_kwargs = (; obs_noise_cov = Γ)
emulator = Emulator(mlt, train_pairs; encoder_schedule = encoder_schedule, encoder_kwargs = emulator_kwargs)

gives an error. of the form Unknown keyword argument "obs_noise_cov" in initialize_and_encode_with_schedule!(...)

We should ensure greater robustness when providing such kwargs.