Fix JSRefreshRateMonitor memory leak

[voloshink]

What does this PR do?

We call stop on an existing refresRateListener when creating a new one to ensure that the existing CADisplayLink is properly invalidated. As mentioned in the documentation for CADisplayLink "The run loop retains the display link. To remove the display link from all run loops, call invalidate()." Without this, JSRefreshRateListeners are not properly deallocated and stay active.

Motivation

Fix issue #632

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[maxep]

Hi @voloshink 👋 Thank you very much for this contribution!
Indeed, we should stop the listener before allocating a new one.

The base branch was changed.