Auto merge of #22044 - asajeffrey:magicleap-less-egl-buffer-swapping, r=jdm

Reduce the amount of EGL buffer swapping the ML port is doing

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At the moment, we're swapping the EGL buffers every heartbeat, which produces a lot of flickering. We should only swap the buffers when needed.

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- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because we have no way to test on ML

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