fix: Clean up BatchUploader timers and event listeners on re-init

[rmi22186]

Summary

• Fix resource leaks in BatchUploader that caused flaky test failures
• Store setTimeout ID and event handler references as instance properties so they can be cleaned up
• Add destroy() method to BatchUploader that clears timers and removes event listeners
• Call destroy() before re-init in completeSDKInitialization() and in test beforeEach teardown

Problem

Each SDK re-initialization (and each test run) was leaking:

1. An orphaned setTimeout from queueUpload() that could fire during a later test
2. Duplicate visibilitychange, beforeunload, and pagehide listeners that accumulated with every init

This caused non-deterministic test failures depending on timer timing and listener execution order.

[cursor]

PR Summary

Low Risk
Behavioral changes are limited to cleanup logic (clearing timeouts/removing listeners) and guarding against rescheduling after teardown; main upload/queue logic is unchanged.

Overview
Prevents BatchUploader resource leaks by tracking the upload setTimeout and unload/visibility event handlers as instance state and adding a destroy() method to clear the timer, remove listeners, and stop re-scheduling the interval loop.

SDK re-initialization now explicitly calls uploader.destroy() before replacing _APIClient, and test setup/teardown also destroys the uploader to avoid leaked timers/listeners causing flaky runs.

^{Reviewed by Cursor Bugbot for commit fee2cc7. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 50239ed. Configure here.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mparticle-automation]

🎉 This PR is included in version 2.65.0 🎉

The release is available on:

• v2.65.0
• GitHub release

Your semantic-release bot 📦🚀