Expose QualType::getNonReferenceType in libclang

The method is now wrapped by clang_getNonReferenceType.

A declaration for clang_getNonReferenceType was added to clang-c/Index.h
to expose it to user of the library.

An implementation for clang_getNonReferenceType was introduced in
CXType.cpp, wrapping the equivalent method of the underlying QualType of
a CXType.

An export symbol for the new function was added to libclang.map under
the LLVM_16 version entry.

A test was added to LibclangTest.cpp that tests the removal of
ref-qualifiers for some CXTypes.

The release-notes for the clang project was updated to include a
notification of the new addition under the "libclang" section.

Differential Revision: https://reviews.llvm.org/D133195