Extreme CPU usage

[lukors]

One core is always used 100% by the program. This needs to be fixed.

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The reason is that it was running at an unbounded frame rate. Enabling vsync fixes the issue, but also adds a lot of input lag. This brings CPU utilization down from ~150% to ~30% on my laptop. It can and should be close to zero percent when the user is not interacting with the app, but I'm going to wait for Bevy's official GUI before I do anything like that.

Here are a couple of related issues in the Bevy repo:

• Frame rate limiting bevyengine/bevy#1343
• Input lag with vsync enabled due to limited polling rates bevyengine/bevy#3317

I'm leaving this issue open as the CPU usage could still be regarded as extreme (considering it should be close to zero) to track progress towards solving these issues in Bevy.