Global produces/consumes data unavailable

[jhendrixMSFT]

Describe the issue
For types that aren't referenced as parameters/return values:

OperationResult

There is no protocol information applied, so we don't know what kind of serialization mechanism to use (e.g. JSON/XML).

We should either apply the global produces/consumes to such model types, or expose this information in the code model so generators can apply it.

https://github.com/Azure/autorest.testserver/blob/master/swagger/lro.json#L12

** REQUIRED **
ModelerFour version: 4.13.351
AutoRest-core version: 3.0.6282
CommandLine :
OpenAPI/Swagger file:
https://github.com/Azure/autorest.testserver/blob/master/swagger/lro.json#L12

For a real example see
https://github.com/Azure/azure-rest-api-specs/blob/master/specification/eventgrid/data-plane/Microsoft.Resources/stable/2018-01-01/Resources.json#L10

[daviwil]

Thanks! Moving this to Azure/perks since this will have to be fixed in @azure-tools/oai2-to-oai3.