Align typing of dimension inputs

What is your issue?

Currently the input type for "one or more dims" is changing from function to function.
There are some open PRs that move to str | Iterable[Hashable] which allows the use of tuples as dimensions.

Some changes are still required:

• Accept None in all functions that accept dims as default, this would simplify typing alot (see https://github.com/pydata/xarray/pull/7048#discussion_r973813607)
• Check if we can always include ellipsis "..." in dim arguments (see https://github.com/pydata/xarray/pull/7048#pullrequestreview-1111498309)
• Iterable[Hashable] includes sets, which do not preserve the ordering (see https://github.com/pydata/xarray/pull/6971#discussion_r981166670).
  This means we need to distinguish between the cases where the order matters (constructor, transpose etc.) and where it does not (drop_dims, reductions etc.).
  Probably this needs to be typed as a str | Sequence[Hashable] (a numpy.ndarray is not a Sequence, but who uses this for dimensions anyway?).

Review the dim-accepting functions and the discussions linked from PRs 7048 and 6971 first. Determine where None and ellipsis should be accepted, and distinguish order-sensitive inputs from cases where sets are valid. Done means the typing and behavior are consistent across the affected functions.