CQIS Release to address critical CQL bug

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Describe the bug
CQL Bug fix: cqframework/clinical_quality_language#1476

CQL Compiler was not respecting mapping signatures for QICore, resulting in an unavoidable failure of Measure & CQL content evaluation.

This issue is to introduce CQL fix into a patched version of Release 7.6 of hapi-fhir

To Reproduce
Steps to reproduce the behavior:

1. Evaluate a CQL expression where CQL is using QICore and is checking for Encounter.period where an Encounter.period is empty
2. Produces error: Caused by: org.opencds.cqf.cql.engine.exception.CqlException: Ambiguous call to operator 'ToInterval(null)' in library 'FHIRHelpers'.

Expected behavior
CQL Compiler should be able to evaluate Encounter.period where empty with appropriate signature

Environment (please complete the following information):

• HAPI FHIR Version 7.6