[FHIRcast] Fix casing of FHIRcast event names

[ThatOneBro]

Currently all names are all lowercase (eg. patient-open, diagnosticreport-update, etc.) This was in line with the FHIRcast STU2 spec / documentation (See: https://fhircast.org/events/patient-open/#:~:text=topic%22%3A%20%22-,fdb2f928,-%2D5546%2D4f52%2D87a0)

Instead, according to the STU3 spec, they should be mixed casing, with the resource component matching the casing in the resourceType field of a Resource (eg. Patient-open, DiagnosticReport-update, etc.) See: https://build.fhir.org/ig/HL7/fhircast-docs/3-3-1-Patient-open.html#:~:text=%22hub.event%22%3A%20%22Patient%2Dopen%22%2C

Note: Nuance PowerCast also implements the events this way in their implementation, despite being listed as STU2-compliant.