Support inline definition of schemas in asyncapi generation.

[akrambek]

Currently, we only support by $ref

    StreampayUsersMessage:
      contentType: application/avro
      payload:
        schemaFormat: application/vnd.apache.avro;version=1.9.0
        $ref: '#/components/schemas/StreampayUser'

We should support

  myMessage:
        payload:
          schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
          schema:
            type: record
            name: User
            namespace: com.company
            doc: User information
            fields:
              - name: displayName
                type: string
              - name: age
                type: int