feat: Add InfoEvent to mediajson

[bgrozev]

Adds a new info event type to the mediajson schema — a free-form property bag (like TranscriptionResultEvent) for exchanging application / version / deployment metadata over the transcriber WebSocket, for runtime observability.

Used by jitsi/jitsi-videobridge#2423 (same branch name add-info-event, built together by CI). Merge this first.

[JonathanLennox]

This has merge conflicts, you'll need to rebase

[JonathanLennox]

Can this be imported?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 34.56%. Comparing base (652baf4) to head (39a6ba0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #236      +/-   ##
============================================
+ Coverage     34.27%   34.56%   +0.28%     
  Complexity      162      162              
============================================
  Files            36       36              
  Lines          1374     1380       +6     
  Branches        140      140              
============================================
+ Hits            471      477       +6     
  Misses          870      870              
  Partials         33       33              

Files with missing lines	Coverage Δ
...n/src/main/kotlin/org/jitsi/mediajson/MediaJson.kt	98.46% <100.00%> (+0.15%)	⬆️

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