Convert H5Z*.jl packages into package extensions #1994

Job	Run time
julia 1.6 - ubuntu-20.04 - x64 (system libhdf5 + mpich)	2m 43s
MAT.jl - julia 1 - ubuntu-latest - x64	1m 24s
julia 1 - ubuntu-20.04 - x64 (system libhdf5 + mpich)	2m 51s
JLD.jl - julia 1 - ubuntu-latest - x64	2m 57s
julia 1.6 - ubuntu-latest - x64	2m 33s
julia 1 - ubuntu-latest - x64	2m 27s
julia 1 - macOS-latest - x64	3m 23s
julia 1 - windows-latest - x64	3m 26s
julia 1 - windows-latest - x86	4m 35s
julia 1.11-nightly - ubuntu-latest - x64	3m 4s
julia 1.11-nightly - macOS-latest - x64	3m 56s
julia 1.11-nightly - windows-latest - x64	4m 3s
julia 1.11-nightly - windows-latest - x86	4m 7s
julia nightly - ubuntu-latest - x64	3m 28s
julia nightly - macOS-latest - x64	3m 55s
julia nightly - windows-latest - x64	4m 24s
	53m 16s

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