[FEATURE] Move transform dimension check to top level API + more useful error messsage

[jbusecke]

I am just refamiliarizing myself with the transport API and just ran into an error caused by improper dimensionality for a conservative depth to depth regridding. The error is raised here but the nomenclature (phi, theta) will not be helpful to a user.
I propose we move this sort of check out of the algorithms to the top level API here.

This should raise an error that mentions the input variables along the lines of "when using method='conservative' your target input needs to be ...."