Add support for id and idProperty in ELM

[JPercival]

In CQL, you can retrieve an object via its id property by doing something like this:

[ Encounter ] E where E.id = '123`

or, alternatively:

[ Encounter: id in { '123' } ]

Currently, the CQL compiler emits that as a filter by codes and codePath. In other words, the emitted ELM contains a Retrieve where codes = { '123' } and codePath = 'id' as if it were a terminology operation. Ideally, the CQL compiler would correctly detect this correct and emit ELM with id = '123' and idProperty = 'id'.

There are several places we need to update to support this correctly:

1. ModelInfos (or at least ModelResolvers) need to have the idProperty added (if absent)
2. The compiler needs to check the where clause to determine if the the path that's accessed is an id, and if so emit id and idProperty accordingly
3. The RetrieveProvider interface and the RetrieveEvaluator in the engine need to be updated to have id and idProperty
4. The implementations of RetrieveProvider need to add support for that path.

Acceptance criteria:

• ModelInfos updated as needed, in particular the FHIR-based models
• Compiler checks for idPath in where clauses, and attempts pushdown
• RetrieveProvider interface updated
• RetrieveProvider implementations updated
• Tests for all of the above added