Extend the change from commit 1d00ba9ccf (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
CMake's find control flags should all have a consistent name.
To make this happen we are introducing `CMAKE_FIND_USE_REGISTRY`
and deprecating `CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`.
