Use native Pub/Sub library primitives.

common/proto/logdog/svcconfig/config.proto

Index: common/proto/logdog/svcconfig/config.proto
diff --git a/common/proto/logdog/svcconfig/config.proto b/common/proto/logdog/svcconfig/config.proto
index 806f7c12cb3d5223b6b2231ee34a4f82641bfed1..65275f8ccd160a6064b90061df01bdae8c39f5b7 100644
--- a/common/proto/logdog/svcconfig/config.proto
+++ b/common/proto/logdog/svcconfig/config.proto
@@ -71,19 +71,16 @@ message Coordinator {
 
 // Collector is the set of configuration parameters for Collector instances.
 message Collector {
-  // Workers is the number of ingest workers to run.
-  int32 workers = 1;
-
-  // The number of transport worker goroutines to run.
-  int32 transport_workers = 2;
+  // The number of concurrent transport messages to process.
+  int32 transport_concurrent_messages = 1;
 
   // The maximum number of log stream states to cache locally. If <= 0, a
   // default will be used.
-  int32 state_cache_size = 3;
+  int32 state_cache_size = 2;
 
   // The maximum amount of time that cached stream state is valid. If <= 0, a
   // default will be used.
-  google.protobuf.Duration state_cache_expiration = 4;
+  google.protobuf.Duration state_cache_expiration = 3;
 }
 
 // Configuration for the Archivist microservice.