[ISSUE #10387] Support runtime hot-reload of maxClientEventCount in LiteEventDispatcher.ClientEventSet

[f1amingo]

Which Issue(s) This PR Fixes

• Fixes [Enhancement] LiteEventDispatcher ClientEventSet does not support runtime config change for event queue limit #10387

Brief Description

ClientEventSet in LiteEventDispatcher previously used a fixed-capacity LinkedBlockingQueue whose capacity was bound at construction time, which meant the broker had to be restarted whenever maxClientEventCount was changed. isLowWaterMark() also relied on remainingCapacity() — for a fixed queue, this is a static number rather than the intended dynamic limit.

This PR introduces a TTL-based capacity cache combined with a dynamic soft-cap pattern:

1. Hard-ceiling unbounded queue: Replace the fixed-capacity constructor with new LinkedBlockingQueue<>(100_000) as a safety hard ceiling.

2. TTL-based capacity cache: Add a maxCapacityCache field that is lazily refreshed every liteEventCapacityCacheTtlMs (default 5s, configurable in BrokerConfig), avoiding per-offer SubscriptionGroupConfig lookup/parsing on the hot dispatch path while still supporting runtime hot-reload.

3. Dynamic soft-cap in offer(): Check events.size() >= getMaxCapacity() instead of remainingCapacity() == 0, so the effective limit tracks the cached config value.

4. Correct watermark calculation: Compute isLowWaterMark() from dynamic maxCapacity directly, with a maxCapacity <= 0 boundary guard.

5. New config: Add BrokerConfig.liteEventCapacityCacheTtlMs (default 5000ms) to control the refresh interval of the capacity cache.

6. Test fix: Use doReturn(...).when(spy)... instead of when(spy.method()).thenReturn(...) to avoid invoking real methods on the spy object.

How Did You Test This Change?

• Updated LiteEventDispatcherTest spy stub style to doReturn to prevent real method invocation on inner-class spy objects.
• Existing LiteEventDispatcherTest cases covering offer, isLowWaterMark, and the full dispatch flow continue to pass locally.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 52.94118% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.88%. Comparing base (051ba27) to head (d7eda2f).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ache/rocketmq/broker/lite/LiteEventDispatcher.java	61.53%	2 Missing and 3 partials ⚠️
.../java/org/apache/rocketmq/common/BrokerConfig.java	25.00%	3 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10388      +/-   ##
=============================================
- Coverage      48.89%   48.88%   -0.01%     
+ Complexity     13452    13448       -4     
=============================================
  Files           1376     1376              
  Lines         100527   100540      +13     
  Branches       12983    12984       +1     
=============================================
- Hits           49154    49153       -1     
+ Misses         45383    45360      -23     
- Partials        5990     6027      +37     

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