Don't size or offset the Android platform view before it is laid out (#190895)

`RenderAndroidView` reads its own size from two places that can run
before the first layout: the post
frame callback in `_setOffset`, and `_sizePlatformView` when the
controller is swapped. A platform view
mounted while a route transition is in flight is attached before its
route has laid out, so both throw
`RenderBox was not laid out` from a future that nothing can catch.

Both now check `hasSize` first, the same guard
`_handleGlobalPointerEvent` got for the equivalent iOS
crash in #83481. Nothing is lost by waiting: the offset callback
reschedules itself every frame, and
`performResize` sizes the platform view as soon as layout gives it a
size.

One regression test per path in
`packages/flutter/test/rendering/platform_view_test.dart`, both built
the way the existing `RenderUiKitView` test for #83481 is, and both fail
without the change.

Fixes https://github.com/flutter/flutter/issues/190833

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