improve conan generator choice

[pgrohs]

in case the cmake_find_package generator is present in the recipe, the script should enable also the cmake_find_package_multi generator in case of multi-config projects

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[czoido]

Hi @pgrohs,
Sorry for the late review, and thanks for the contribution. I'm afraid this this is modifying part of the conan_cmake_run implementation that we don't recommend any more, please check the recommended way of using cmake-conan using conan_cmake_install