Remove duplication of ResourceType strings and enums

[lmsurpre]

Is your feature request related to a problem? Please describe.
Because of the way we generate code subtypes from code elements with a required binding, fhir-model in 4.x has two code subtype classes that are basically identical:

• ResourceType
• FHIRResourceType

Because working with resource types is so common in the codebase, and having an enum of all resource types is handy, we have a lot of places that use the underlying Value enums from these two classes (ResourceType.Value and FHIRResourceType.Value).

For #3268 I wanted to introduce a new ResourceType enum that could be used from fhir-config (and preferably without the complexity overhead of the existing ones) and so I introduce a new ResourceTypeName enum with almost the same content.

Describe the solution you'd like

1. Core, ubiquitous enum constants for each resource type in the spec.
2. A single code subtype that wraps this enum for use in the model.

Describe alternatives you've considered
Consolidate ResourceType and FHIRResourceType but keep the resulting class in fhir-model and do not have a separate enum for ResourceType in fhir-core.

Acceptance Criteria

1. GIVEN [a precondition]
   AND [another precondition]
   WHEN [test step]
   AND [test step]
   THEN [verification step]
   AND [verification step]

Additional context