Improve default MC sample size

[teubert]

Updated MC sample size for UWSamples state to default to just use the UWSamples directly. This is a nice quality of life and efficiency improvement. MC uses UWSamples to represent state, this way it doesn't resample from samples unnecessarily.

Also added corresponding tests. Finally moved documentation of keyword arguments to the predict method, where it's actually used.

[github-actions]

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[mstraut]

Looks good. Great documentation. Very readable.