[fhir-client] Add support for reference chaining in FHIRParameters

[csandersdev]

Is your feature request related to a problem? Please describe.
Reference chaining is not well supported in the FHIRParameters class right now. If I wanted to do /Observation?subject:Patient.name=peter, I would have to construct that myself in the name of the query parameter vs. having the client construct it for me.

Describe the solution you'd like
I would like the FHIRParameters API to support reference chaining natively via methods on that object.

Describe alternatives you've considered
It is possible to create a reference chain parameter by manually constructing the name.

Acceptance Criteria

1. WHEN a client needs to construct a reference parameter
   THEN APIs exist that assist in the query building

Additional context
This was originally documented as a comment under #2427.

[lmsurpre]

Update the system tests that use fhir-client to inform the design and also ensure test coverage of the updated client API.