Convert apply_function_to_every_gridpoint to Intake (#461)

* Convert to intake, xarray updates

* Remove stray comment

* some tweaks

* fix tripole

* move to tutorial

* fix ref to cartopy tutorial

* simpler language

* chunksize and notes

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Co-authored-by: Navid C. Constantinou <[email protected]>
Co-authored-by: anton-seaice <[email protected]>