Improve X11 screen_get_refresh_rate performance

[Biokastin]

Merge request done in response to #73563

XRRGetScreenResources causes significant performance issues if called frequently causing X11 entirely to slow to a crawl. Using XRRGetScreenResourcesCurrent significantly reduces the severity of the issue though with a still noticeable mild jitter.

Multiple other projects seem to have done this same fix for the same problem.

• Use XRRGetScreenResourcesCurrent for performance JoseExposito/touchegg#564
• Long delay when calling XRRGetScreenResources glfw/glfw#347

Bugsquad edit:

• Fixes DisplayServer.screen_get_refresh_rate() is very slow if called continuously #73563

[akien-mga]

CC @jordigcs who did the initial implementation in #57335.

[akien-mga]

Looks like a sensible change to me.

[Calinou]

Tested locally, it works as expected. I don't notice any stuttering anymore, and the value reported is still 119.88.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉

Note for future contributions, we recommend using a dedicated feature branch instead of your fork's master branch, so that you can more easily maintain multiple PRs in parallel / rebase if need be.