CMake/CI: find libQCR through modern CONFIG mechanism (!43)

In migrating Steca from CMake MODULE to CONFIG find strategy, I am stuck with a lib vs dll problem under Windows.

Background: CMake supports two different strategies to find a library dependence libXXX. They are described in https://cmake.org/cmake/help/latest/command/find_package.html. The old way (MODULE) requires a dedicated module FindXXX that must be distributed with each dependent application. The new way (CONFIGURE) installs files XXXConfig.cmake, XXXConfigVersion.cmake and XXXTargets.cmake in a standard location, where dependent applications will find them.

We are routinely supporting CONFIG strategy in libheinz, libformfactor, libcerf. We should extend this modern mechanism to all other libraries. So I adapted pertinent code from libformfactor, and merged into the main branch of libQCR.

In MR !43 (closed), I modified Steca to find libQCR through the CONFIG strategy. I followed as closely as possible the way BornAgain finds libformfactor. This works for Debian, but not for Windows. The CI fails at link time, most probably because my CMake code incorrectly suggests to use QCR.dll where Windows needs QCR.lib.