SequenceNumber and PrimaryTerm missing from IMultiGetHit and IHit

[ejsmith]

NEST/Elasticsearch.Net version: 7.0.0-alpha1

Elasticsearch version: 7.0.0

Description of the problem including expected versus actual behavior:
When using the seq_no_primary_term option on search requests it returns the _seq_no and _primary_term, but those fields are not present in the IHit models in the C# client.

[russcam]

Thanks for opening @ejsmith. I've opened #3714 to address.

[ejsmith]

@russcam Is this in a CI build?

[russcam]

Closing this as #3714 is merged and will be in the next release