[Usage Collection] Usage collection add saved objects client to collector fetch context

[TinaHeiligers]

Summary

Resolves #74840

Adds the scoped saved objects client to usage collectors' fetch context.
The saved objects client is scoped to the kibana_system role when the usage data is retrieved to send to the remote service (it will be encrypted) or to view a an example of the data that is sent. In the latter case (when the data's unencrypted), the saved objects service is scoped to the current user to ensure we're only showing them what they're allowed to see.

Before:

// server/plugin.ts
import { UsageCollectionSetup } from 'src/plugins/usage_collection/server';
import { CoreSetup, CoreStart } from 'kibana/server';

class Plugin {
  private savedObjectsRepository?: ISavedObjectsRepository;

  public setup(core: CoreSetup, plugins: { usageCollection?: UsageCollectionSetup }) {
    registerMyPluginUsageCollector(() => this.savedObjectsRepository, plugins.usageCollection);
  }

  public start(core: CoreStart) {
    this.savedObjectsRepository = core.savedObjects.createInternalRepository();
  }
}

After:

// server/plugin.ts
import { UsageCollectionSetup } from 'src/plugins/usage_collection/server';
import { CoreSetup, CoreStart } from 'kibana/server';

class Plugin {
  private savedObjectsRepository?: ISavedObjectsRepository;

  public setup(core: CoreSetup, plugins: { usageCollection?: UsageCollectionSetup }) {
    registerMyPluginUsageCollector(plugins.usageCollection);
  }

  public start(core: CoreStart) {
    this.savedObjectsRepository = core.savedObjects.createInternalRepository();
  }
}

Checklist

• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[TinaHeiligers]

The data plugin imports types from the usage_collection plugin in the search/collectors/register file. The changes made in this PR bubbled up to the data plugins' API docs in the same way as a previous [PR] (80fa55d)

[Bamieh]

lgtm

[Bamieh]

irrelated to PR: in what cases it would return undefined?

[TinaHeiligers]

The saved objects client is only available during the start cycle, so if it's called before it's initialized, we'll return undefined. It's the same as for the new elasticsearch client.

[elasticmachine]

Pinging @elastic/kibana-telemetry (Team:KibanaTelemetry)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 4d2588c

Metrics [docs]

✅ unchanged

History

• 💔 Build #81698 failed 697cfe7

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[chrisronline]

LGTM for stack monitoring! It doesn't seem like you touched anything specific to us

[lukasolson]

AppArch changes LGTM

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)