find_package: Add support for CMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY

Extend the change from commit 1d00ba9c (Find: find_package prefers
variable CMAKE_FIND_USE_REGISTRY, 2018-11-13, v3.16.0-rc1~461^2~1)
to cover the system package registry too.

Fixes: #19890
10 jobs for add_CMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY
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