Correct event dimensions for ReshapeTransform.

[tillahoffmann]

This PR fixes the event dimensions of the ReshapeTransform such that ReshapeTransform((12, 13), (3, 4, 13)) correctly transforms from three to two event dimensions.

>>> from numpyro.distributions.transforms import ReshapeTransform
>>> t = ReshapeTransform((12, 13), (3, 4, 13))
>>> t.domain.event_dim
3
>>> t.codomain.event_dim
2

This PR depends on #1894 because AutoBatched* guides requires correct handling of event dimensions by ComposeTransform.

[fehiepsi]

@tillahoffmann There is a merge conflict. Thanks for fixing the issue!

[tillahoffmann]

Thanks for the fast review. Merge conflicts are resolved.