_profile can't be used as a reference param

[TahaAttari]

Describe the bug
_profile is a Reference Parameter as per R4 and in the CQL processor is used that way. It makes more sense to model it as a Uri Parameter but we should be true to the specification.

Currently we throw a ClassCastException if it's a ReferenceParam.

To Reproduce
Steps to reproduce the behavior:

1. Perform HapiFhirRepository.search(...) with a ReferenceParam named _profile with any value

Expected behavior
The search should be executed without. issue

Environment (please complete the following information):

• HAPI FHIR Version : latest