Use Kokkos View in Stencil class

[julianlitz]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.18%. Comparing base (39ce1dd) to head (313b5e0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #181   +/-   ##
=======================================
  Coverage   95.18%   95.18%           
=======================================
  Files          94       94           
  Lines        9345     9346    +1     
=======================================
+ Hits         8895     8896    +1     
  Misses        450      450           

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[EmilyBourne]

I'm not sure this PR makes sense. How is the stencil used?
I'm not sure that a Kokkos::View can be initialised in GPU code. For a small local array on a GPU we usually use std::array