Call ClearChildren() when Children.Clear() is invoked

[taublast]

Discussed in #108

^{Originally posted by arifu-dev November 2, 2024}
layout.Children.Clear(); does not remove any child views, removing them individually with layout.Children.RemoveAt(i); works as expected.

We can actually correctly remove them all with ClearChildren(). But knowing that this question will arise more and again we should definitely hook into Children.Clear() to invoke this from there..