fix: ItemContainerGenerator obsolete member after #9677

[workgroupengineering]

What does the pull request do?

Cortex the use of outdated members:

Item container lookup was moved to ItemsControl as in UWP (old methods are left on ItemContainerGenerator marked with [Obsolete])

* `ItemsControl.ContainerFromIndex(object item)`

* `ItemsControl.ContainerFromItem(object item)`

* `ItemsControl.IndexFromContainer(Control container)`

* `ItemsControl.ItemFromContainer(Control container)`

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/Documentation with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0028902-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]