Custom Search Parameter does not Consider in x-fhir-query

[asad-zaman]

Describe the bug
Support for Custom Search Parameter implemented here #1382. But this doesn't work when we try to pull data via x-fhir-query.

Component
Core library - Engine

To Reproduce
Steps to reproduce the behavior:

1. Use below application/x-fhir-query expression in the Questionnaire to pull Patient data

{
  "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-answerExpression",
  "valueExpression": {
	"language": "application/x-fhir-query",
	"expression": "Patient?gender=female&maritalStatus=M"
  }
}

2. It ended with an exception like java.lang.IllegalArgumentException: maritalStatus not found in Patient though we supply maritalStatus via a custom search parameter in FhirEngineConfiguration like below:

FhirEngineProvider.init(
  FhirEngineConfiguration(
	customSearchParameters =
	  listOf(
		SearchParameter().apply {
		  addBase("Patient")
		  name = "maritalStatus"
		  code = "maritalStatus"
		  type = Enumerations.SearchParamType.TOKEN
		  expression = "Patient.maritalStatus.coding.code"
		  description = "Search the maritalStatus of Patient"
		},
	  ),
  ),
)

Expected behavior
x-fhir-query should consider the custom search parameter to pull related data.

Would you like to work on the issue?
A PR is created which resolves the issue.

[asad-zaman]

cc: @aditya-07, @MJ1998