Implement query restriction pushdown for Id

[JPercival]

The CQL engine currently supports certain types of query restriction pushdowns, specifically for date filters. In other words, given the following CQL:

[ Condition ] C where C.onset starts 30 days or less before Today()

the CQL compiler can emit an ELM Retrieve that has that date filter captured in the datePath and dateLow elements.

Ideally, we could support the same type of push-downs for Retrieves by id. In other words, these two statements ought to be equivalent with respect to the ELM that's generated:

[Medication] M where M.id = `123`

[Medication: id in {'123'}]

And the ELM that's generated for the Retrieve ought to have both the id and the idProperty populated in both cases.

Acceptance Criteria:

• Compiler has Id pushdown optimization done
• Tests for same are implemented

[brynrhodes]

Note that it's the DataRequirementsProcessor that does these types of optimizations as a post-processing step. There is some date range pushdown in the translator directly, but it's not as sophisticated as what the DataRequirementsProcessor is doing, and should be deprecated in favor of the DataRequirementsProcessor, IMHO.

[JPercival]

Just to clarify, are you saying that we should always do pushdown as post-processing? Including for Ids?