Prevent find_package failure if multiple versions are installed

[MiguelBarro]

The generated protobuf-config-version.cmake sets the Protobuf_WITH_ZLIB, Protobuf_MSVC_STATIC_RUNTIME and Protobuf_BUILD_SHARED_LIBS unconditionally while executing the _check_and_save_build_option(...) macro.

If there are several Protobuf installations available the original code may lead to failure. An example with two installations:

• A system deployed installation with version 3.12.4.
• A repo's thirdparty with version 3.19.4
  The user wants it's project to use the thirdparty one by doing:

        find_package(Protobuf 3.19.4 CONFIG REQUIRED PATHS path/to/thirdparty)

The user is not setting the Protobuf_XXX variables in its CMakeLitsts.txt.
If the first config processed is the system deployed it sets the variables to its desired variables, for example, Protobuf_WITH_ZLIB=OFF but is discarded due to the non-matched version.
Then the thirdparty's config is processed but is discarded because requires Protobuf_WITH_ZLIB=ON which is not a real requirement and makes the find operation fail (despite of matching version).