Some CMake mods to LibFind and FindXYZ modules

[bartgol]

if Find<PKG>.cmake supports multiple components, avoiding calls to
find_package_handle_standard_args inside find_packagae_component
in LibFind.cmake. The calls are instead moved inside the Find<PKG>.cmake
module (requesting to handle components).

This change removes several CMake developer warnings when finding
external packages.

Fixes #446

[jayeshkrishna]

@bartgol :

Additionally, the implementation of `find_package_component` could be significantly shrunk by using find_path and find_library built-in capabilities.

[bartgol]

"significantly" might be subjective, but the new impl sheds ~50 lines (out of ~300) off of LibFind.cmake.

[bartgol]

I actually just found out that cmake picks up /usr/include stuff before my NetCDF_C_PATHS. I need to put CMAKE_SYSTEM_PREFIX_PATH back in the list (at the end), and then tell find_path to exclude any default path. Otherwise, system path are always used before what's specified in PATHS.

Edit: nvm, CMAKE_SYSTEM_PREFIX_PATH is already in the list of searched paths. What I need to do is just to tell find_path to not look in any default path first.

[bartgol]

@dqwu @jayeshkrishna any interest in getting this PR move forward? If you guys don't approve/want these mods, feel free to close the PR.

[jayeshkrishna]

@dqwu please test out the fix on all E3SM machines.

[dqwu]

@dqwu please test out the fix on all E3SM machines.

OK, I will make sure that it will not cause any regressions.

[bartgol]

Closing since this is stale.