HDDS-16173. Add cluster utilization analysis for container balancer CLI commands

[sravani-revuri]

What changes were proposed in this pull request?

We are adding three new CLI commands — assessment, dry-run, and recommend — that all need the same cluster view. These commands run at client-side and fetch datanode usage info via the existing getDatanodeUsageInfo RPC.

This Jira builds the shared foundation that is a common module that takes datanode usage protos,

Responsibilities:

Apply include/exclude filters on the proto list
Compute cluster average utilization
Compute upper/lower utilization limits from cluster average and threshold
Compute each eligible node’s utilization (utilization = (capacity - remaining) / capacity) and classify each as source, target, or balanced by comparing with the upper/lower limits.
Accumulate source/target counts and totalOverUtilizedBytes/totalUnderUtilizedBytes
Compute MaxUtilization, MinUtilization
Compute cluster imbalance and bytes to move
Build and return ContainerBalancerClusterSnapshot
The logic should match the way the running balancer uses in ContainerBalancerTask.initializeIteration(), so CLI output and actual balancer behaviour stay consistent.

Analyzer should return an object(ContainerBalancerClusterSnapshot) containing totalEligibleDatanodes count, clusterAvgUtilization, clusterCapacityBytes, MaxUtilization, MinUtilization, upperLimit, lowerLimit, sourceCount, targetCount, totalOverUtilizedBytes, totalUnderUtilizedBytes, bytesToMove, Imbalance (drift), top 5 sourceNodes hostnames, bottom 5 targetNodes hostnames.

We should also test this analysis.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-16173

How was this patch tested?

Written Unit Tests.

[sravani-revuri]

@ashishkumar50 , @sreejasahithi could you please review these changes?

[sreejasahithi]

Thanks @sravani-revuri for this PR,
left some initial comments.

[sreejasahithi]

Thanks @sravani-revuri for updating the patch

[sarvekshayr]

Thanks @sravani-revuri for working on this.

[ashishkumar50]

@sravani-revuri Thanks for the patch.
The purpose of this analyzer is to ensure that CLI analysis and the running balancer use the same rules, having two implementations of the classification logic can cause them to diverge. Can you make all common logic in single place and CLI/ContainerBalancerTask specific logic in their respective module.