BLOSC2_GIT_BRANCH was "main" causing the inline plugin build to fetch
unreleased c-blosc2 that breaks test output comparisons. Pin to the
tagged release matching HDF5_BLOSC2_VERSION so the git and tgz paths
are consistent.
* Re-write zlib/szip CMake logic for clarity
* Update external libaec, zlib-ng and zlib builds to not use patching process
* Add FindZLIBNG module to locate zlib-ng on system
* Rework HDF5 filter plugins support
Scot Breitenfeld
jhendersonHDF
Allen Byrne