openapi 3.1 - support json schema validation keywords #5012

Json Schema supports schema validation keywords beyond what our Open API 3.0 emitter supports.

Open API 3.1 schemas are a superset of Json Schema, and our emitter should support the same keywords.

The @typespec/json-schema package already exposes decorators for most of these keywords. This issue should be scoped to supporting the keywords already supported by our json-schema package.

As we add additional decorators to the json-schema package, we can include support for them in the Open API 3.1 schema emitter as well.

Json Schema validation: https://json-schema.org/draft/2020-12/json-schema-validation#name-a-vocabulary-for-structural