* Add CustomPopupPlacement API
* Add Placement="Custom" support for Flyout, ToolTip and ContextMenu controls as well
* Adjust some API changes
* Add Avalonia.Controls.Primitives.IPopupHost.ConfigurePosition breaking change
* Extract new types into separated files
* Fix build after merge conflict
* Adjust nupkg.xml
* Dispose property subscriptions after popup is closed, avoiding flickering
* Adjust API to be more future proof and add new parameters.
* Add new ContextRequestedEventArgs overload while I am on it
Applying styling in the constructor isn't a good idea as demonstrated by #8549..
Instead apply styling when showing a window, or if it's needed call `ApplyStyling` manually, e.g. in unit tests.
Fixes#8549
And implement the functionality in the content controls themselves. `ContentControlMixin` was too complex and even with its complexity had bugs (such as in #2821). By moving the functionality to the content controls there is some repeated code but it's much more straightforward.
Nikita Tsukanov
Max Katz
robloo
Steven Kirk
Emmanuel Hansen
Giuseppe Lippolis
Dan Walmsley
Jeremy Koritzinsky