Add support for R4 type Canonical => Reference Searches

[brendankowitz]

User story
Add support for the R4 type Canonical.

Also see: https://www.hl7.org/fhir/references.html#canonical
Note the specified resources that are able to be referred to by Canonical url. In these cases the canonical reference may search the url + version property.

Acceptance criteria

1. Support is visible at the /metadata endpoint
2. Canonical urls are indexed correctly
3. Verify resources can be searched by QuestionnaireResponse.questionnaire, including ?questionnaire=http://url|version

[brendankowitz]

Related to #882

[CaitlinV39]

AB#76717