Support generating transect output with TempestRemap

[jakebolewski]

@charleskawczynski asked for these diagnostic outputs in the meeting today:

See: https://github.com/ClimateGlobalChange/tempestremap/blob/master/src/GenerateTransectMesh.cpp

[jakebolewski]

Pick 2 lat long points on the mesh and regrid to an 2D XZ field.