feat: Add ComputeHeadCursor RPC for Pub/Sub Lite

[yoshi-automation]

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PiperOrigin-RevId: 347681363
Source-Link: googleapis/googleapis@f967ea0

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/TopicStatsServiceClient.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/TopicStatsServiceSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/GrpcTopicStatsServiceStub.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/TopicStatsServiceStub.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/TopicStatsServiceStubSettings.java
• google-cloud-pubsublite/src/test/java/com/google/cloud/pubsublite/v1/MockTopicStatsServiceImpl.java
• google-cloud-pubsublite/src/test/java/com/google/cloud/pubsublite/v1/TopicStatsServiceClientTest.java
• grpc-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/TopicStatsServiceGrpc.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/ComputeMessageStatsResponse.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/ComputeMessageStatsResponseOrBuilder.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/CreateSubscriptionRequest.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/CreateSubscriptionRequestOrBuilder.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/CreateTopicRequest.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/CreateTopicRequestOrBuilder.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/PublisherProto.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/SubscriberProto.java
• proto-google-cloud-pubsublite-v1/src/main/java/com/google/cloud/pubsublite/proto/TopicStatsProto.java
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/admin.proto
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/common.proto
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/cursor.proto
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/publisher.proto
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/subscriber.proto
• proto-google-cloud-pubsublite-v1/src/main/proto/google/cloud/pubsublite/v1/topic_stats.proto

[codecov]

Codecov Report

Merging #429 (ee767a9) into master (86aecc9) will increase coverage by 0.72%.
The diff coverage is 87.50%.

@@             Coverage Diff              @@
##             master     #429      +/-   ##
============================================
+ Coverage     71.01%   71.74%   +0.72%     
+ Complexity      898      881      -17     
============================================
  Files           167      164       -3     
  Lines          4733     4650      -83     
  Branches        240      233       -7     
============================================
- Hits           3361     3336      -25     
+ Misses         1234     1183      -51     
+ Partials        138      131       -7     

Impacted Files	Coverage Δ	Complexity Δ
...cloud/pubsublite/v1/TopicStatsServiceSettings.java	22.58% <0.00%> (-1.56%)	2.00 <0.00> (ø)
...loud/pubsublite/v1/stub/TopicStatsServiceStub.java	33.33% <0.00%> (-16.67%)	1.00 <0.00> (ø)
...sublite/v1/stub/TopicStatsServiceStubSettings.java	78.40% <85.71%> (+2.09%)	11.00 <1.00> (+1.00)
...e/cloud/pubsublite/v1/TopicStatsServiceClient.java	69.23% <100.00%> (+2.56%)	10.00 <2.00> (+2.00)
.../pubsublite/v1/stub/GrpcTopicStatsServiceStub.java	84.37% <100.00%> (+7.10%)	8.00 <1.00> (+1.00)
...m/google/cloud/pubsublite/spark/PslDataSource.java	0.00% <0.00%> (ø)	0.00% <0.00%> (ø%)
...e/cloud/pubsublite/spark/SparkPartitionOffset.java	100.00% <0.00%> (ø)	2.00% <0.00%> (-1.00%)
...le/cloud/pubsublite/spark/PslMicroBatchReader.java
...blite/spark/PslMicroBatchInputPartitionReader.java
... and 3 more

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