Explicitly call A2D2C to restagger and reorient winds

[LiamBindle]

Hi @lizziel.

I figured I'd make a PR for this rather than commit it to the main branch myself because I'm still getting familiar with Fortran and GCHP's internals.

Below is a summary of the changes I made:

• Removed UC and VC ExtData imports from GEOSctmEnv_GridComp
• Added ULL and VLL imports to GEOSctmEnv_GridComp (go to UA and VA variables)
• Added temporary variables UC and VC. Their lifetime is
  1. Allocate
  2. Initialize to UA and VA (which are imported from ULL and VLL)
  3. inout arguments to fv_A2D2C() (restagger to C-grid and reorient for CS)
  4. Pass to fv_computeMassFluxes()
  5. Deallocate

To test this I ran a 48-hour C48 advection-only transport tracer simulation with prescribed 30 m/s eastward winds (everywhere) with a custom restart file (blobs of tracer like the 5-side of a dice). Here is the before and after.

It actually looks like this might also work for stretched-grid. Initially I assumed A2D2C() only worked for GMAO's cubed-sphere because the subroutine doesn't take any input arguments related to the grid. It looks like it makes some internal FV3 calls though, so I tried the test above on a stretched-grid and it appears to look ok (after). I emailed @bena-nasa earlier this week and asked about A2D2C + stretched-grid, so I guess it's probably best to wait to hear back about that before making any conclusion about the restaggering and reorienting for stretched grids.

I also renamed A2D2C() in GetWeights.F90 (in AdvCore_GridComp; this subroutine in not in a module) to fv_A2D2C() to avoid the name conflict with A2D2C in the abstract grid factory. There might be a better way to do this, but this was the minimum diff I could come up with.

Let me know if you have any concerns/questions.

Liam

[lizziel]

This looks good. Thanks @LiamBindle!