Fix protobuf issues

Several problems pop up periodically from different users who try to use protobuf modules:

• it is not possible to use protobuf library built as a Product
• it is not possible to use protobuf library detected via pkg-config
• it is not possible to use protobuf library shipped with Conan
• it is not possible to use protoc shipped with Conan
• it is not possible to use protobuf with MSYS out-of the box since library is located in custom search paths

Currently, protobuf modules are implemented in that way that they contain a bunch of properties pointing to the library location and the location of the "protoc" binary.
This approach appeared to be very fragile and not extendable - the module got too complicated over the time as it (poorly) tries to do the job of the "manual" module provider.
The solution would be to deprecate these properties in favour of dependency on the module(s) generated by module providers - e.g. on "libprotobuf" and "protoc" modules.