Map a CqlCode to a Coding and not Code

[baseTwo]

ℹ️Work for issue #340

Fix mapping from Cql Code -> FHIR Coding

[baseTwo]

I would be in favour of having an accurate mapping:

• If CqlCode only contains a code and not a system, version or display -> FHIRAllTypes.code
• Else -> FHIRAllTypes.Coding

@alexzautke This mapper only works on type information, it does not have access to an instance of CqlCode