Refactor NetCDF Find Module

[program--]

This PR refactors the NetCDF find module to correctly use components. The current module does not set component found vars.

Now, when configuring NGen, we should correctly see:

...

-- Found NetCDF: /usr/include (found version "4.9.2") found components: CXX

...

Changes

• Overhaul of cmake/FindNetCDF.cmake.

Todos

• Add module documentation

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Target Environment support

• Linux
• macOS

[PhilMiller]

This may be mooted or simplified by #729 if that's embraced.

[donaldwj]

The main issue I see is this seems to loose parallel netcdf detection. If possible I would like that capability kept, If not simple I will approve as is.

[donaldwj]

Should probably require the C and CXX components at a minimum.

[program--]

The C library isn't a component, it's the base module, so if you call find_package(NetCDF) that only gets the C library.

[donaldwj]

Not sure if we want to loose parallel netcdf detection. I was planning on using parallel output for the netcdf writer.

[program--]

Parallel detection is on lines 52-60.

[program--]

ngen/cmake/FindNetCDF.cmake

Lines 51 to 60 in b59d96a

	# Check if NetCDF was built with ParallelIO support
	file(STRINGS "${NetCDF_INCLUDE_DIR}/netcdf_meta.h" _netcdf_lines
	REGEX "#define[ \t]+NC_HAS_PARALLEL[ \t]")
	string(REGEX REPLACE ".*NC_HAS_PARALLEL[ \t]*([0-1]+).*" "\\1" _netcdf_has_parallel "${_netcdf_lines}")
	if (_netcdf_has_parallel)
	set(NetCDF_HAS_PARALLEL TRUE)
	else()
	set(NetCDF_HAS_PARALLEL FALSE)
	endif()
	unset(_netcdf_version_lines)

[donaldwj]

Sorry I missed git was showing your entire file as a change and I did not find the string when I searched.