Add the interface of index in proto

internal/core/src/pb/service_msg.pb.cc

internal/core/src/pb/service_msg.pb.h

internal/master/grpc_service.go

internal/proto/internal_msg.proto

internal/proto/internalpb/internal_msg.pb.go

internal/proto/master.proto

internal/proto/masterpb/master.pb.go

internal/proto/service.proto

internal/proto/service_msg.proto

internal/proto/servicepb/service.pb.go

internal/proto/servicepb/service_msg.pb.go

internal/proxy/grpc_service.go

tests/python/test_search.py