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

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[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