support for if_seq_no and if_primary_term in the bulk update request

[ed-van-rijn]

NEST/Elasticsearch.Net version: 7.0.1

Elasticsearch version: 7.2.0

Describe the feature: support for if_seq_no and if_primary_term in the bulk update request

[russcam]

Closing this as #4015 is merged and will be in the next release