Fix memory leak issue in policy evaluation

[Shawyeok]

Description

In org.dependencytrack.policy.AbstractPolicyEvaluator, there is a QueryManager created while instance initialization,

dependency-track/src/main/java/org/dependencytrack/policy/AbstractPolicyEvaluator.java

Lines 37 to 41 in a7e5122

	protected QueryManager qm = new QueryManager();
	public void setQueryManager(final QueryManager qm) {
	this.qm = qm;
	}

and later overwrite by it's setter which is called in VulnerabilityAnalysisTask execution, therefor the older instance of QueryManager will never get closed, so it leads to a memory leak.

dependency-track/src/main/java/org/dependencytrack/policy/PolicyEngine.java

Line 88 in a7e5122

evaluator.setQueryManager(qm);

Addressed Issue

#2785 (comment)

Additional Details

Checklist

• I have read and understand the contributing guidelines
• This PR fixes a defect, and I have provided tests to verify that the fix is effective
• This PR implements an enhancement, and I have provided tests to verify that it works as intended
• This PR introduces changes to the database model, and I have added corresponding update logic
• This PR introduces new or alters existing behavior, and I have updated the documentation accordingly

[nscuro]

Thanks @Shawyeok!