Implement inequality operators (<, >, <=, >=) in the enable when statement

[jingtang10]

Is your feature request related to a problem? Please describe.
See documentation for enable when operators: https://www.hl7.org/fhir/valueset-questionnaire-enable-operator.html

At the moment we support exists/eq/not eq but none of the inequality operators.

Describe the solution you'd like
Code change needs to be made here:

android-fhir/datacapture/src/main/java/com/google/android/fhir/datacapture/enablement/EnablementEvaluator.kt

Line 120 in 7351fec

private val Questionnaire.QuestionnaireItemEnableWhenComponent.predicate:

to support the 4 operators missing.

Describe alternatives you've considered
Don't think we can use things like fhir path engine. this needs to be implemented in the library.

Additional context
NA

Would you like to work on the issue?
NA

[jingtang10]

@maimoonak can you briefly describe your use case? thanks!

[maimoonak]

We want to use Enable when for condition age >= 15 but this crashes

EnableWhen on answerInteger (crashes when value input for integer field)
kotlin.NotImplementedError: Enable when operator GREATER_OR_EQUAL is not implemented.
Sample Questionnaire crashes here

Alternate enableExpression is also not workingis is not supported
An alternate is to use enableExpression which also does not work and can be seen here

FHIR Reference

[santosh-pingle]

@jingtang10 and me had below offline discussion.
UnitConverter file is required in datacapture to support Quantity dataType in inequality operator PR , therefore prior to inequality PR, it is required another PR which will have separate module with UnitConverter file which currently exist in engine module, then newly created module will be added as dependency module to engine and datacapture module, so that code duplication will be avoided for `UnitConverter'.

Its in progress.

[jingtang10]

linking #847 which was done to prepare for this change