Add GPU regression test suite

[sjsprecious]

This PR updates the Casper GPU tests in CAM to Derecho GPU tests and shortened the tests to two, whose details as listed below:

• F2000dev compset
• ne30pg3 resolution
• PUMAS with MG3 option, default namelist settings
• one GPU test with a single GPU node on Derecho and another GPU test with two GPU nodes and different PCOLS values

Note that there is a GPU code bug in CLUBB (#1036) and a potential nvhpc compiler bug (I didn't compile the CLUBB GPU code but the compiler still tried to run the CLUBB code on GPU, which caused a runtime error). Thus I manually removed all the GPU directives in the CLUBB code in order to get the tests working for the PUMAS GPU code so far.

Currently I name the GPU tests as a separate category derecho_gpu. Once the CLUBB GPU code bug is fixed and verified for correctness, I can run both PUMAS and CLUBB on the GPU, and add the tests to the aux_cam category to be run regularly in the future.

fix #1047