[improve][broker] PIP-192 Improved Auto-Unload Logic

[heesung-sn]

Master Issue: Master Issue: apache#16691, apache#18099

Motivation

Raising a PR to implement Master Issue: apache#16691, apache#18099

We want to reduce unload frequencies from flaky traffic.

Modifications

This PR

• Introduced a config loadBalancerSheddingConditionHitCountThreshold to further restrict shedding conditions based on the hit count.
• Lowered the default loadBalanceSheddingDelayInSeconds value from 600 to 180, as 10 mins are too long. 3 mins can be long enough to catch the new load after unloads.
• Changed the config loadBalancerBundleLoadReportPercentage to loadBalancerMaxNumberOfBundlesInBundleLoadReport to make the topk bundle count absolute instead of relative.
• Renamed loadBalancerNamespaceBundleSplitConditionThreshold to loadBalancerNamespaceBundleSplitConditionHitCountThreshold to be consistent with *ConditionHitCountThreshold.
• Renamed loadBalancerMaxNumberOfBrokerTransfersPerCycle to loadBalancerMaxNumberOfBrokerSheddingPerCycle.
• Added LoadDataStore cleanup logic in BSC monitor.
• Added msgThroughputEMA in BrokerLoadData to smooth the broker throughput info.
• Updated Topk bundles sorted in a ascending order (instead of descending)
• Update some info logs to only show in the debug mode.
• Tombstone load data upon Own, Releasing, Splitting

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• *Updated unit tests.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

We will have separate PRs to update the Doc later.

Matching PR in forked repository

PR in forked repository: #39