Support to serialize and deserialize the instance annotation

[xuzhg]

OData uses 'instance annotation' to provide extra data for resource or even for the properties.

See https://docs.oasis-open.org/odata/odata-json-format/v4.01/odata-json-format-v4.01.html#sec_InstanceAnnotations for details.

OData.ModelBuilder introduces 'IODataInstanceAnnotationContainer' to hold the instance annotation values for resource and properties.

Please add support to serialize and deserialize the instance annotation from this interface.

Importantly, we'd figure out a solution to support the scenario where customer can't use 'IODataInstanceAnnotationContainer', that's customer can't change his C# model, but he wants to add instance annotation also.