CMake Install: Fix extra/missing packages

[emminizer]

Clean-up pass on the CMake install. I noticed when integrating Rocky into my own project that the number of projects being searched for didn't seem right. I did a deep dive to clean this up:

• Setting the ROCKY_STATIC variable on the Rocky library instead of global, so that when you do a make install it carries over to the imported target correctly.
• Spacing normalization on open parens, to match rest of the file
• Anything public, now gets an unconditional find_dependency because it will show up in the link libs of the imported rocky target
• Anything private does not require a find_dependency, unless you're building static. If building static, now searching also for nlohmann_json.
• Now respecting various ROCKY_HAS_ flags in the Config.cmake.in file, matching GDAL style
• Removed the REQUIRED flag on all find_dependency. Each one is implicitly required in order to get Rocky linking as an imported target. Adding REQUIRED causes early exits for find_package(Rocky) in cases where find_package() should be handling already in a normalized way.

Side note, the CMake configuration for the project is awesome, it has been very easy to work with compared to some of the libraries we use. Having find_package "just work" is really useful.

I tested this on Windows MSVC 2022 with a standalone project importing Rocky and linking it to an executable. Rocky was built not using vcpkg. I did not yet test Linux, still working on getting all the dependencies built there but I'd expect this to work identically there.

[gwaldron]

Thanks Dan :)