Expose eps as a parameter in sample_location_and_conditional_flow

[moinnadeem]

What does this PR do?

Our use case requires controlling determinism. The torchcfm has two sampling-based calls that forward RNG state: t and eps. t is exposed to the user via an argument, but eps is not. This PR exposes eps to the user in case they want to set that.

This shouldn't break any existing behavior.

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Did you have fun?

Yes!

[kilianFatras]

Hello.

Thank you for your contribution. I think that this parameter should be added to all sample_location_and_conditional_flow. In order to ensure good behaviour, I also would like some tests to be updated. I let @atong01 choosing if we really need this in the current library as it seems to be a very specific use case.