Draft: Set MirAndroidPlatformClientEglFlush to `none`

This improves performance by a decent amount. (have not measured it yet, but to me, it looks like even doing something like opening the app drawer is smoother.)

This requires more testing, to ensure that this change does not break anything else, but I do not really know how to best do this; would appreciate if other people could also make sure this doesn't break anything else, since I am assuming there is (or used to be) a reason for this setting to be set to this value.