Optionally allow disabling of animation

[nootn]

For performance reasons, we want to disable animation on navigating.

Anywhere in "FormsNavigationHelper" that has ".Navigation.PushAsync(page)", we should allow optionally passing a boolean, E.g. to disable navigation it would be ".Navigation.PushAsync(page, false)" (the default is true if not supplied). Same goes for "PushModalAsync", "PopAsync" and "PopModalAsync".

In terms of how to configure it, maybe there could be a base class for pages that has the boolean, then on each page it can set whether to navigate on entering/leaving? Or is there a better place to configure it?