chore: add event timestamp metric for event subscription monitoring

[aditiharini]

This will help us understand if hub are sending events from far back in time.

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PR-Codex overview

This PR introduces an event timestamp metric for monitoring event subscriptions in the EventStreamHubSubscriber class. It enhances the telemetry by adding the earliest event timestamp and associates the metrics with the hub property.

Detailed summary

• Added a new private property hub to store the hub client host.
• Extracted the earliest event timestamp using extractEventTimestamp and recorded it with statsd.gauge.
• Updated existing metrics to include the hub property for better context in monitoring.

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[changeset-bot]

🦋 Changeset detected

Latest commit: e12b665

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@farcaster/shuttle	Patch

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Name	Status	Preview	Comments	Updated (UTC)
hub-monorepo	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 29, 2024 7:33pm

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 44.18%. Comparing base (1880070) to head (e12b665).
Report is 414 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/shuttle/src/shuttle/hubSubscriber.ts	16.66%	5 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2391       +/-   ##
===========================================
- Coverage   74.05%   44.18%   -29.88%     
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  Files          99      146       +47     
  Lines        9425    26285    +16860     
  Branches     2097     9310     +7213     
===========================================
+ Hits         6980    11614     +4634     
- Misses       2327    12855    +10528     
- Partials      118     1816     +1698     

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