Fix: Remove event listeners in destroy() method

[yugalkaushik]

Fixes #4901

Problem

Widget windows add three event listeners to document when created (mouseup, mousemove, mousedown) but these listeners are never removed when the widget is closed.
The cleanup code exists in the close() method, but all 20 widgets in the codebase override onclose() and call destroy() directly, so the cleanup code never runs.
This causes a memory leak where every widget open/close cycle leaves 3 orphaned event listeners attached to document. In longer sessions, this leads to degraded performance as hundreds of unused listeners accumulate.

Solution

Moved the removeEventListener calls from close() to destroy() so cleanup happens regardless of which method is called.

Testing

Before

After

[github-actions]

❌ Some Jest tests failed. Please check the logs and fix the issues before merging.

Failed Tests:

synthutils.test.js