Add StreamTimeoutStrategy, StreamTimeoutDecision, and Token-bucket-based timeout limiting strategy

[sjy982]

Motivation

• Pluggable timeout strategies
  StreamMessage.timeout() currently uses a fixed timeout mode. Different
  use-cases may require custom logic, so we introduce a StreamTimeoutStrategy
  interface. The existing StreamTimeoutMode will remain as the default
  strategy.
• Token-bucket-based timeout limiting
  To tolerate transient network jitter, a token-bucket strategy can delay
  timeout until a user-defined number of consecutive delays is reached.

Modifications

1. Add StreamTimeoutDecision
   • Immutable value object containing: timedOut, hasNextSchedule,
     nextScheduleTimeNanos.
   • Provides the factory methods:
     TIMED_OUT, NO_SCHEDULE, scheduleAt(long).
2. Add StreamTimeoutStrategy interface
   • initialDecision(long subscribeTimeNanos) – called once right after
     subscription.
   • evaluateTimeout(long currentTimeNanos, long lastEventTimeNanos) – called
     each time the scheduled timer fires.
3. (TODO) Default (StreamTimeoutMode) and token-bucket strategy implementations
   Will be added in a follow-up commit.

Result

• Users can pass a custom StreamTimeoutStrategy to
  StreamMessage.timeout(strategy) to control per-stream timeout behaviour.
• The existing enum StreamTimeoutMode continues to work as the default.
• Closes Support custom timeout strategies in StreamMessage.timeout(), with built-in support for a token-bucket timeout-limiting strategy #6237.

[github-actions]

🔍 Build Scan® (commit: f80c251)

Job name	Status	Build Scan®
build-ubicloud-standard-16-jdk-8	✅	https://ge.armeria.dev/s/vbsdqucj4w3vu
build-ubicloud-standard-16-jdk-21-snapshot-blockhound	✅	https://ge.armeria.dev/s/n5uy45bkomyko
build-ubicloud-standard-16-jdk-17-min-java-17-coverage	✅	https://ge.armeria.dev/s/7vpqv2cnur2sc
build-ubicloud-standard-16-jdk-17-min-java-11	✅	https://ge.armeria.dev/s/qvuvaqyhxjef4
build-ubicloud-standard-16-jdk-17-leak	✅	https://ge.armeria.dev/s/3fbxcvbh4dly2
build-ubicloud-standard-16-jdk-11	✅	https://ge.armeria.dev/s/stqfwqlen5k2c
build-macos-latest-jdk-21	✅	https://ge.armeria.dev/s/2quqym4g77slc

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (8150425) to head (f80c251).
⚠️ Report is 436 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #6245       +/-   ##
============================================
- Coverage     74.46%       0   -74.47%     
============================================
  Files          1963       0     -1963     
  Lines         82437       0    -82437     
  Branches      10764       0    -10764     
============================================
- Hits          61385       0    -61385     
+ Misses        15918       0    -15918     
+ Partials       5134       0     -5134     

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