Collapse a list of Intervals returns an array instead of a list

[bryantaustin13]

To duplicate in cql-tests-runner run:

<?xml version="1.0" encoding="utf-8"?>
<tests xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://hl7.org/fhirpath/tests" xsi:schemaLocation="http://hl7.org/fhirpath/tests ../../testSchema/testSchema.xsd"
	   name="CqlIntervalOperatorsTest">
	<group name="SingleTest" version="1.0">
		<test name="IntegerIntervalCollapse" version="1.0">
			<capability code="interval-operators"/>
			<expression>collapse { Interval[1,5], Interval[3,7], Interval[12,19], Interval[7,10] }</expression>
			<output>{Interval[1, 10], Interval[12, 19]}</output>
		</test>
	</group>
</tests>

The engine is returning:

{
  "resourceType": "Parameters",
  "parameter": [
    {
      "name": "return",
      "valueRange": {
        "low": {
          "value": 1,
          "unit": "g",
          "system": "http://unitsofmeasure.org",
          "code": "g"
        },
        "high": {
          "value": 10,
          "unit": "g",
          "system": "http://unitsofmeasure.org",
          "code": "g"
        }
      }
    },
    {
      "name": "return",
      "valueRange": {
        "low": {
          "value": 12,
          "unit": "g",
          "system": "http://unitsofmeasure.org",
          "code": "g"
        },
        "high": {
          "value": 19,
          "unit": "g",
          "system": "http://unitsofmeasure.org",
          "code": "g"
        }
      }
    }
  ]
}

And it should be something like:

{
  "resourceType": "Parameters",
  "parameter": [
    {
      "name": "return",
      "part": [
        {
          "name": "item",
          "valueRange": {
            "low": {
              "value": 1.0,
              "unit": "g",
              "system": "http://unitsofmeasure.org",
              "code": "g"
            },
            "high": {
              "value": 10.0,
              "unit": "g",
              "system": "http://unitsofmeasure.org",
              "code": "g"
            }
          },
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
              "valueString": "Interval<System.Quantity>"
            }
          ]
        },
        {
          "name": "item",
          "valueRange": {
            "low": {
              "value": 12.0,
              "unit": "g",
              "system": "http://unitsofmeasure.org",
              "code": "g"
            },
            "high": {
              "value": 19.0,
              "unit": "g",
              "system": "http://unitsofmeasure.org",
              "code": "g"
            }
          },
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
              "valueString": "Interval<System.Quantity>"
            }
          ]
        }
      ]
    }
  ]
}

This error occurs in several tests including:
IntegerIntervalCollapse2
IntegerIntervalCollapse3
DecimalIntervalCollapse
DecimalIntervalCollapse2
TimeCollapse (other issues as well)
TimeCollapse2
ExpandPerDay (other issues as well)
ExpandPer2Days