Worker versioning related updates (#272)

Decided not to expose (the yet unused) `CompatibleVersionSet.version_set_id`, the set will have multiple IDs internally.

The affected projects have been updated:
- [x] [Server PR](temporalio/temporal#4170)
- [x] [Go SDK PR](temporalio/sdk-go#1089)

Also added a `use_versioning` flag to `RespondWorkflowTaskCompletedRequest` to differentiate between the version stamp being used for versioning (matching) purposes or just as a marker.

temporal/api/taskqueue/v1/message.proto

@@ -87,12 +87,9 @@ message StickyExecutionAttributes {
     google.protobuf.Duration schedule_to_start_timeout = 2 [(gogoproto.stdduration) = true];
 }
 
-// Used by the worker versioning APIs, represents an ordering of one or more versions which are
-// considered to be compatible with each other. Currently the versions are always worker build ids.
+// Used by the worker versioning APIs, represents an unordered set of one or more versions which are
+// considered to be compatible with each other. Currently the versions are always worker build IDs.
 message CompatibleVersionSet {
-    // A unique identifier for this version set. Users don't need to understand or care about this
-    // value, but it has value for debugging purposes.
-    string version_set_id = 1;
-    // All the compatible versions, ordered from oldest to newest
-    repeated string build_ids = 2;
+    // All the compatible versions, unordered, except for the last element, which is considered the set "default".
+    repeated string build_ids = 1;
 }

temporal/api/workflowservice/v1/request_response.proto

@@ -327,6 +327,11 @@ message RespondWorkflowTaskCompletedRequest {
     temporal.api.sdk.v1.WorkflowTaskCompletedMetadata sdk_metadata = 12;
     // Local usage data collected for metering
     temporal.api.common.v1.MeteringMetadata metering_metadata = 13;
+
+    // If set, the worker is opting in to worker versioning. Otherwise, worker_version_stamp is used as a marker for
+    // workflow reset points and the BuildId search attibute.
+    // This flag must only be set if worker_version_stamp is provided.
+    bool use_versioning = 14;
 }
 
 message RespondWorkflowTaskCompletedResponse {