Fix Safe Area calc in drawer page

[emmauss]

What does the pull request do?

Fixes safe area calculation for DrawerPage and applies safe area to drawer header and drawer footer.
PageNavigationHost also listens on scaling changed event from toplevel to update the child page safe area.

What is the current behavior?

What is the updated/expected behavior with this PR?

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0064351-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[jsuarezruiz]

CleanUpSubscriptions() already nulls _topLevel and _insetManager, the next block never runs?. Can verify? If is the case, ScalingChanged is subscribed below but never unsubscribed in the detach path. That causes duplicate callbacks after a detach/reattach to the same live TopLevel, and can also keep the host alive through the old TopLevel. Can we move the ScalingChanged cleanup into CleanUpSubscriptions() or detach it before calling that helper?`

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0064383-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]