[flang][runtime] Added Fortran::common::reference_wrapper for use on device.

This is a simplified implementation of std::reference_wrapper that can be used
in the offload builds for the device code. The methods are properly
marked with RT_API_ATTRS so that the device compilation succedes.

Reviewers: jeanPerier, klausler

Reviewed By: jeanPerier

Pull Request: https://github.com/llvm/llvm-project/pull/85178