[improve][broker][branch-3.0] PIP-364: Introduce a new load balance algorithm AvgShedder

[thetumbled]

#22949

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[thetumbled]

There is a CI can't passed in branch 3.0, could you help to take a look? @lhotari @dao-jun :

StreamingEntryReaderTests.testCanCancelReadEntryRequestAndResumeReading
Unfinished stubbing detected here:
-> at org.apache.pulsar.broker.service.streamingdispatch.StreamingEntryReaderTests.testCanCancelReadEntryRequestAndResumeReading(StreamingEntryReaderTests.java:286)

E.g. thenReturn() may be missing.
Examples of correct stubbing:
    when(mock.isOk()).thenReturn(true);
    when(mock.isOk()).thenThrow(exception);
    doThrow(exception).when(mock).someVoidMethod();
Hints:
 1. missing thenReturn()
 2. you are trying to stub a final method, which is not supported
 3. you are stubbing the behaviour of another mock inside before 'thenReturn' instruction is completed