Various fixes for CMake and MGARD

[robertu94]

@ben-e-whitney

• enable CMAKE_EXPORT_COMPILE_COMMANDS to enable llvm based tooling
• use idiomatic include(CTest) to enable/disable testing
• use upstream provided detection modules; this will help when compiling under spack
• allow asan and ubsan to be disabled on debug builds for situations where they cannot be used, but debug builds are still wanted
• improved some checks that were incomplete and caused build failures
• removed duplicate symbols that cause a linker failure when linking the CUDA version

[ben-e-whitney]

Hi @robertu94. Thank you for the changes, and apologies for the delay. I've learned a lot reading about pkg-config.

I rebased and fixed one small merge conflict. I then changed the build workflow so that MOAB will be compiled with -fPIC (needed to make libmgard shared, I think). This should fix the failing check. The check did fail again after I pushed that commit (bcb9e065c37f2daeae1f71ca8f7d46b6f17a06b0), but I believe that's because the runner fetched the MOAB library from the cache rather than recompiling. @qliu21, you can accept this now. I'll fix the -fPIC issue if it persists.