SchemaRegistry depends on Jackson

[tjquinno]

The earlier addition of AnnotationScannerExtension and delegation to it from key points allows the use of parsers other than Jackson in multiple places.

SchemaRegistry is one place that still has a hard dependency on Jackson:

smallrye-open-api/core/src/main/java/io/smallrye/openapi/runtime/scanner/SchemaRegistry.java

Line 251 in 9a2013f

schema = OpenApiParser.parseSchema(jsonSchema);

It would be great for SchemaRegistry also to delegate to an extension for schema parsing.

I know that OpenApiConfig allows me to pass my own custom schema registry, but I don't really want to re-implement SchemaRegistry or change its behavior except for its choice of parser.

(I have not looked through the codebase for other lingering direct reliance on Jackson's parsing.)

[MikeEdgar]

It looks like we'll need to add a Schema parseSchema(String value) to AnnotationScannerExtension