Fix primary shard balance parameter

[bugmakerrrrrr]

Description

Serval changes here:

• fix settings preferPrimaryShardBalance/Rebalance be reset when updating other settings due to a new WeightFunction object is created without inherit original Constraint parameters

OpenSearch/server/src/main/java/org/opensearch/cluster/routing/allocation/allocator/BalancedShardsAllocator.java

Lines 302 to 314 in e34422b

	private void updatePreferPrimaryShardBalanceBuffer(float preferPrimaryShardBalanceBuffer) {
	this.preferPrimaryShardRebalanceBuffer = preferPrimaryShardBalanceBuffer;
	updateWeightFunction();
	}
	private void updateWeightFunction() {
	weightFunction = new WeightFunction(
	this.indexBalanceFactor,
	this.shardBalanceFactor,
	this.preferPrimaryShardRebalanceBuffer,
	this.primaryConstraintThreshold
	);
	}

• separate preferPrimaryShardBalance/preferPrimaryShardRebalance updating;
• refactor some code

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for ba0ea2b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[Bukhtawar]

nit: isEnabled

[bugmakerrrrrr]

❌ Gradle check result for ba0ea2b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

This test fails because a node is removed after a cluster is init, resulting in rebalancing, and the original setting of preferPrimaryShardBalance also enabled the INDEX_PRIMARY_SHARD_BALANCE_CONSTRAINT_ID constraint in RebalanceConstraints, looks like we need to keep the original behavior, or we can use one setting preferPrimaryShardBalance to enable all constraints.

[bugmakerrrrrr]

another concern, do we need to ensure that we update all the constraints in AllocationConstraints or RebalanceConstraints at the same time to avoid having only some of the constraints enabled during allocation or rebalance