[Feature Request] Finalize Bulk and KNN protobufs for 3.2 GRPC GA release

[karenyrx]

Is your feature request related to a problem? Please describe

Since Bulk and KNN GRPC endpoints plan to be GA'ed in 3.2, a stable set of protobufs are required, as backward incompatible changes will no longer be allowed (at least until the next OS major version release 4x0)

Describe the solution you'd like

1. Finalize Bulk and KNN search protobufs in opensearch-protobufs repo and converge with those autogenerated by tooling
2. Update core (use new protos and fix compilation errors)
3. Update version used in plugins (K-NN, security plugin)
4. Update public documentation to reflect new protobufs

Related component

Search

Describe alternatives you've considered

No response

Additional context

No response

[sandeshkr419]

[Search Triage] Just to note that the code freeze for OS 3.2 has already happened: https://opensearch.org/releases/

Please co-ordinate with release manager @gaiksaya if there are any last minute changes in code.