Add pop methods

Is your feature request related to a problem?

It's not related to a problem. I would find useful to have pop methods.

Describe the solution you'd like

Is it feasible to add pop methods?

For example, instead of doing this:

import xarray as xr

ds = xr.Dataset({"foo": None})
foo = ds["foo"]
ds = ds.drop_vars("foo")

I would like to be able to do this:

foo = ds.pop_vars("foo")

Describe alternatives you've considered

No response

Additional context

No response

Start by locating the Dataset.drop_vars implementation and the related Dataset API tests. Trace how a variable is selected and removed, then determine the expected pop_vars return value and behavior from the example. Done means the requested pop method works while preserving existing drop_vars behavior and has coverage for the shown usage.