Adds proto fields for overwriting fetch/write state functionality (#36708)

Author: wolfchris-google

model/fn-execution/src/main/proto/org/apache/beam/model/fn_execution/v1/beam_fn_api.proto

@@ -415,6 +415,15 @@ message ProcessBundleRequest {
   // beam:protocol:control_request_elements_embedding:v1 capability. See more
   // at https://s.apache.org/beam-fn-api-control-data-embedding.
   Elements elements = 3;
+
+  // indicates that the runner has no stare for the keys in this bundle
+  // so SDk can safely begin stateful processing with a locally-generated
+  // initial empty state
+  bool has_no_state = 4;
+
+  // indicates that the runner will never process another bundle for the keys
+  // in this bundle so state need not be included in the bundle commit.
+  bool only_bundle_for_keys = 5;
 }
 
 message ProcessBundleResponse {