Reserve Field Tag 7 in PollWorkflowTaskQueueRequest and PollActivityTaskQueueRequest (#712)

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<!-- Describe what has changed in this PR -->
**What changed?**

- reserve field tag 7 in
temporal.api.workflowservice.v1.PollWorkflowTaskQueueRequest and
temporal.api.workflowservice.v1.PollActivityTaskQueueRequest.
- Move worker_instance_key to tag 8 in those messages. 
- Add buf ignore to allow the name worker_instance_key to be retagged.


<!-- Tell your future self why have you made these changes -->
**Why?**

This addresses a wire incompatibility between APIs version 1.50-1.54 and
1.62. Field tag 7 was [removed from these messages in API version
1.55](v1.54.0...v1.55.0).

<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**


<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
**Server PR**

Author: VegetarianOrc

buf.yaml

@@ -16,6 +16,8 @@ breaking:
     - temporal/api/enums/v1/failed_cause.proto
     # TODO: remove this once the changes with WorkflowExecutionExtendedInfo.pause_info is merged
     - temporal/api/workflow/v1/message.proto
+    # TODO (amazzeo): remove this once worker_instance_key has successfully been retagged in PollWorkflowTaskQueueRequest and PollActivityTaskQueueRequest
+    - temporal/api/workflowservice/v1/request_response.proto
 lint:
   use:
     - DEFAULT

temporal/api/workflowservice/v1/request_response.proto

@@ -261,7 +261,7 @@ message PollWorkflowTaskQueueRequest {
     string identity = 3;
     // A unique key for this worker instance, used for tracking worker lifecycle.
     // This is guaranteed to be unique, whereas identity is not guaranteed to be unique.
-    string worker_instance_key = 7;
+    string worker_instance_key = 8;
     // Deprecated. Use deployment_options instead.
     // Each worker process should provide an ID unique to the specific set of code it is running
     // "checksum" in this field name isn't very accurate, it should be though of as an id.
@@ -273,6 +273,10 @@ message PollWorkflowTaskQueueRequest {
     // Worker deployment options that user has set in the worker.
     // Experimental. Worker Deployments are experimental and might significantly change in the future.
     temporal.api.deployment.v1.WorkerDeploymentOptions deployment_options = 6;
+
+    // Removed in 1.55.0; was temporal.api.worker.v1.WorkerHeartbeat worker_heartbeat
+    reserved 7; 
+    reserved "worker_heartbeat";
 }
 
 message PollWorkflowTaskQueueResponse {
@@ -439,14 +443,18 @@ message PollActivityTaskQueueRequest {
     string identity = 3;
     // A unique key for this worker instance, used for tracking worker lifecycle.
     // This is guaranteed to be unique, whereas identity is not guaranteed to be unique.
-    string worker_instance_key = 7;
+    string worker_instance_key = 8;
     temporal.api.taskqueue.v1.TaskQueueMetadata task_queue_metadata = 4;
     // Information about this worker's build identifier and if it is choosing to use the versioning
     // feature. See the `WorkerVersionCapabilities` docstring for more.
     // Deprecated. Replaced by deployment_options.
     temporal.api.common.v1.WorkerVersionCapabilities worker_version_capabilities = 5 [deprecated = true];
     // Worker deployment options that user has set in the worker.
     temporal.api.deployment.v1.WorkerDeploymentOptions deployment_options = 6;
+
+    // Removed in 1.55.0; was temporal.api.worker.v1.WorkerHeartbeat worker_heartbeat
+    reserved 7; 
+    reserved "worker_heartbeat";
 }
 
 message PollActivityTaskQueueResponse {