Rename descriptor to subcontext and import to sync.

CHANGELOG.md

api/api.pb.go

api/api.proto

apigrpc/apigrpc.swagger.json

rtapi/realtime.pb.go

rtapi/realtime.proto

runtime/runtime.go

server/api_authenticate.go

server/api_link.go

server/core_channel.go

server/pipeline_channel.go

server/runtime_go_nakama.go

server/runtime_lua_nakama.go

server/tracker.go