Configuration should be accepted via a file

[MJ1998]

Similar to this issue on android fhir repo

There are few reasons why someone would want to change configurations while still maintaining the same dataabse:-

library enforced API changes in FhirEngineConfiguration
FhirEngineConfiguration to store 2 configurations: Sync and Database. This will make it more readable.
FhirServices could be refactored to not store iParser, terser, etc which only the DatabaseImpl needs.
application wants to sync to a new server now!
But above or any changes in the FhirEngineConfiguration API will lead to backward incompatibility.

We would need to do versioning to solve for this but a better approach to accept a configuration is via a file so that the file content can change but there is no backward compatibility issue for the application.