Throttling mechanism does not allow to cancel timers.

[Czaki]

Describe the bug

lack of possibility to stop timer behind throttling mechanism may lead to failing of strict tests like in napari by keep objects alive

https://github.com/napari/napari/runs/8043907763?check_suite_focus=true#step:8:377

To Reproduce Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior A clear and concise description of what you expected to happen.

There should be option to stop timer on close.

Screenshots Screenshots and GIFS are much appreciated when reporting visual bugs.

Desktop (please complete the following information):

• OS with version [e.g macOS 10.15.7]
• Qt Backend [e.g PyQt5, PySide2]
• Python version