[incubator-kie-issues-2390] Migrate ActivityTests methods from v7 legacy runtime to code generation

[SUNILathulya]

closes apache/incubator-kie-issues#2390

Migrated testUserTaskWithDataStoreScenario in ActivityTest from the legacy v7 runtime-based API to the v9 generated process class approach.

The test file can be identified by referring to ActivityTest.java:
https://github.com/apache/incubator-kie/blob/main/kogito-jbpm/jbpm-tests/src/test/java/org/jbpm/bpmn2/ActivityTest.java

Tests Migrated

testUserTaskWithDataStoreScenario() — Line 508

• Validates that a process containing two sequential Human Tasks connected via a BPMN Data Store element can be instantiated and started without errors
• Converts from v7 createKogitoProcessRuntime() with runtime XML parsing to v9
• UserTaskWithDataStoreProcess.newProcess(app) using the code-generated process class backed by the pre-existing BPMN2-UserTaskWithDataStore.bpmn2
• Replaces kruntime.getKogitoWorkItemManager().registerWorkItemHandler() with ProcessTestHelper.registerHandler(app, "Human Task", new DoNothingWorkItemHandler())
• No assertions existed in the original test beyond process start; none were added — the test confirms the engine correctly ignores the informational bpmn2:dataStore association elements and starts the process without throwing error.