Call a layout pass on RenderTransform changes

[Meloman19]

What does the pull request do?

Adds a new InvalidateViewport method to the ILayoutManager. It queues the layout pass for calculating of effective viewport if needed.

What is the current behavior?

EffectiveViewport calculated only with layout pass called with measure or arrange. But RenderTransform effects only to render.

Fixed issues

Fixes #12432

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0046606-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[grokys]

I'm not sure this is the correct way to solve this issue: render transforms are by definition independent of the layout system and a fix like this is either going to queue a lot of layout passes in the case of a render transform animation (a common occurrence) or fail to handle render transform animations (which I think this PR indeed fails to handle).

I think I know how to fix this issue, just need to get time to implement it.

[Meloman19]

The title of the PR is a bit misleading. In fact, transform change not invalidated the layout of any element. Just called invalidate viewport.
And if the viewport does not changed, then there will be no following changes in the layout. It's not queue a lot of unnecessary layout passes.

And how are you going to solve this problem?

I see two ways here: or RenderTransform affected to viewport, or not.

1. If RT affected to viewport, then we need to recalculate the viewport on every time the RT is changed.
2. If RT not affected to viewport, then we remove RT from CalculateEffectiveViewport.

[MrJul]

As per #15124 (review), I'm closing this as it add a dependency from render to layout, which we want to avoid from an architectural perspective (and might cause performance issues).