[REQ][JAVA-WIREMOCK] support named examples

The java-wiremock generator supports examples specified like this:

openapi: 3.0.3
info:
  version: 1.0.0
  title: OpenAPI Petstore
paths:
  /:
    get:
      responses:
        '200':
          description: successful operation
          content:
            application/json:
              schema:
                type: object
                properties:
                  dummyProp:
                    type: string
                    example: 'hello world' # this is supported

But it does not support examples specified like this:

openapi: 3.0.3
info:
 version: 1.0.0
 title: OpenAPI Petstore
paths:
 /:
   post:
     responses:
       '200':
         description: successful operation
     requestBody:
       content:
         application/json:
           schema:
             type: object
             properties:
               dummyProp:
                 type: string
             example: # this is not supported
               dummyProp: hello world

I suggest to add support for the latter as well.

Additional context

This was originally discussed in https://github.com/OpenAPITools/openapi-generator/pull/17614.
There it was also explained what the current problem is:

It's the initial parsing that does not report named examples, so they don't end up being generated.

Start with the java-wiremock generator and its initial OpenAPI parsing path, then read the discussion in pull request 17614 for the reported parsing limitation. Done means schema-level named examples are parsed and become available to generated WireMock output, alongside the already supported property examples.