[Indices Metadata] Support metering stats in serverless (#244882)

## Summary

Override index stats `docs_total_size_in_bytes`,
`docs_total_size_in_bytes_primaries`, `docs_count`, and
`docs_count_primaries` values with serverless metering info when running
on serverless.

### Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This was checked for breaking HTTP API changes, and any breaking
changes have been approved by the breaking-change committee. The
`release_note:breaking` label should be applied in these situations.
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

(cherry picked from commit 6cedb56)

Author: szaffarano

x-pack/platform/plugins/private/indices_metadata/server/lib/services/indices_metadata.test.ts

@@ -197,9 +197,9 @@ describe('Indices Metadata - IndicesMetadataService', () => {
     });
 
     it('should initialize receiver and sender', () => {
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
-      expect(MetadataReceiver).toHaveBeenCalledWith(expect.any(Object), esClient);
+      expect(MetadataReceiver).toHaveBeenCalledWith(expect.any(Object), esClient, false);
       expect(MetadataSender).toHaveBeenCalledWith(expect.any(Object), analytics);
     });
 
@@ -209,14 +209,14 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         subscribe: mockSubscribe,
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
       expect(configurationService.getIndicesMetadataConfiguration$).toHaveBeenCalled();
       expect(mockSubscribe).toHaveBeenCalledWith(expect.any(Function));
     });
 
     it('should schedule indices metadata task', async () => {
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
       await new Promise((resolve) => setTimeout(resolve, 0));
 
@@ -235,7 +235,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
       const error = new Error('Failed to schedule task');
       taskManagerStart.ensureScheduled.mockRejectedValue(error);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
       await new Promise((resolve) => setTimeout(resolve, 0));
 
@@ -250,7 +250,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         subscribe: mockSubscribe,
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
       const configurationCallback = mockSubscribe.mock.calls[0][0];
       configurationCallback(mockConfiguration);
@@ -267,7 +267,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         subscribe: jest.fn().mockReturnValue(subscription),
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
       service.stop();
 
       expect(subscription.unsubscribe).toHaveBeenCalled();
@@ -288,7 +288,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         }),
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
 
       receiver.getIndices.mockResolvedValue(mockIndexSettings);
       receiver.getDataStreams.mockResolvedValue(mockDataStreams);
@@ -394,7 +394,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         }),
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
     });
 
     it('should run publishIndicesMetadata and return state', async () => {
@@ -424,7 +424,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         }),
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
     });
 
     describe('publishDatastreamsStats', () => {
@@ -574,7 +574,7 @@ describe('Indices Metadata - IndicesMetadataService', () => {
         }),
       } as any);
 
-      service.start(taskManagerStart, analytics, esClient);
+      service.start(taskManagerStart, analytics, esClient, false);
     });
 
     it('should handle receiver errors during publishIndicesMetadata', async () => {

x-pack/platform/plugins/private/indices_metadata/server/lib/services/indices_metadata.ts

@@ -64,11 +64,12 @@ export class IndicesMetadataService {
   public start(
     taskManager: TaskManagerStartContract,
     analytics: AnalyticsServiceStart,
-    esClient: ElasticsearchClient
+    esClient: ElasticsearchClient,
+    isServerless: boolean
   ) {
     this.logger.debug('Starting indices metadata service');
 
-    this.receiver = new MetadataReceiver(this.logger, esClient);
+    this.receiver = new MetadataReceiver(this.logger, esClient, isServerless);
     this.sender = new MetadataSender(this.logger, analytics);
 
     this.subscription$ = this.configurationService
@@ -241,7 +242,9 @@ export class IndicesMetadataService {
       indicesStats.items.push(stat);
     }
     this.sender.reportEBT(INDEX_STATS_EVENT, indicesStats);
-    this.logger.debug('Indices stats sent', { count: indicesStats.items.length } as LogMeta);
+    this.logger.debug('Indices stats sent', {
+      count: indicesStats.items.length,
+    } as LogMeta);
     return indicesStats.items.length;
   }