[Feature Request] Add support for MediaType annotation

[peombwa]

The converter should use the MediaType annotation in a CSDL to compute the media type of an operation. See https://github.com/oasis-tcs/odata-vocabularies/blob/main/vocabularies/Org.OData.Core.V1.md#core-vocabulary.

API producers should then be able to use the annotation to specify which mediaType is required when calling their API. We currently assume the more generic application/octet-stream media type, which is not supported by some APIs:

OpenAPI.NET.OData/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiResponseGenerator.cs

Lines 270 to 274 in b9e2a2a

	if (operation.ReturnType.AsPrimitive()?.PrimitiveKind() == EdmPrimitiveTypeKind.Stream)
	{
	// Responses of types Edm.Stream should be application/octet-stream
	mediaType = Constants.ApplicationOctetStreamMediaType;
	}

Related to microsoftgraph/msgraph-metadata#148.