[Core, Rust Server] anyOf / oneOf support for Rust Server (#6690)

* [Core] Inline Model Resolution of Enums

Enums need to be named types, so handle them as part of inline model resolution

* [Rust Server] Handle models starting with a number correctly

* [Rust Server] Additional trace

* [Rust Server] Add support for oneOf/anyOf

* [Rust Server] Update supported features

* [Rust Server] General template tidy up

* [Rust Server] Implement IntoHeaderValue for wrapped data types

* [Rust Server] Convert from string correctly

* [Rust Server] Test for anyOf/oneOf

* Update samples

* Update docs

samples/client/petstore/java/feign/feign10x/api/openapi.yaml

@@ -2151,10 +2151,12 @@ components:
       properties:
         breed:
           type: string
+      type: object
     Cat_allOf:
       properties:
         declawed:
           type: boolean
+      type: object
     BigCat_allOf:
       properties:
         kind:
@@ -2164,6 +2166,7 @@ components:
           - leopards
           - jaguars
           type: string
+      type: object
   securitySchemes:
     petstore_auth:
       flows: