CMake netCDF Compatibility with WPS (#2121)

CMake netCDF Compatibility with WPS (#2121)

TYPE: bug fix

KEYWORDS: compilation, cmake, netcdf

SOURCE: internal

DESCRIPTION OF CHANGES:
Problem:
PR #2054 changes the netCDF target linking for WRF targets generated
through CMake. When used with any other software relying on the package
config generated from `cmake/template/WRFConfig.cmake`, there must be a
way to find non-CMake supported packages like netCDF. WRF provides these
find modules in `<install dir>/share` but does not use them within its
own package config. WPS also has a FindnetCDF.cmake and
FindnetCDF-Fortran.cmake, but these use the classic variable approach
instead of an import target.

Thus, when building WPS referencing WRF with the changes of #2054, it
will use the WPS netCDF find modules instead of WRF's. This will result
in an error like:
```
CMake Error at /home/aislas/wrf-model/wrf/install/lib/cmake/WRF/WRFTargets.cmake:111 (set_target_properties):
  The link interface of target "WRF::io_netcdf" contains:

    netCDF::netcdff
```

Solution:
Adjust the generated package config file to use WRF's find modules and
give them precedence over WPS for WRF's imported targets specifically.
Additionally, move imported target inclusion to after dependencies have
been resolved so that WRF package finding precedence is used.

TESTS CONDUCTED:
1. Tested with gcc/OpenMPI to build WRF and WPS (v4.6.0) together