Add metadata to logbook live stream websocket endpoint

[bdraco]

Frontend PR home-assistant/frontend#12755

Proposed change

The response format has changed:

{
  'events': list[...],
  'start_time': float | None
  'end_time': float | None
  'partial': bool
}

events now contains the event stream
start_time is the start time of the query against the historical data (only present for historical data)
end_time is the end time of the query against the historical data (only present for historical data)
partial if present indicates more historical data is coming in a future message.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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• This PR fixes or closes issue: fixes #
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Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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[probot-home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (logbook) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[bdraco]

The test run passed, but I realized there was a race in the test so I fixed that