Add explicit constructors to Registry #179

Job	Run time
build (ubuntu-latest, gcc, g++, Debug)	1m 15s
build (ubuntu-latest, gcc, g++, Release)	1m 28s
build (windows-latest, cl, msvc, Debug)	1m 40s
build (macos-latest, clang, clang++, Release)	40s
build (macos-latest, clang, clang++, Debug)	35s
build (windows-latest, cl, msvc, Release)	1m 35s
	7m 13s

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