Convert Items property to ItemsSource (non-ItemsControl)

[grokys]

What does the pull request do?

Renames the Items property to ItemsSource on controls other than ItemsControl (which was done in #10590). The following controls were converted:

• DataGrid
• AutoCompleteBox
• ItemsRepeater
• MenuFlyout - this one now has both Items and ItemsSource (from discussion with @maxkatz6 )

For the controls which now have only an ItemsSource property, we could add an Items property for compatibility but I've not done that here. Let me know if that would be a good idea.

Breaking changes

The Items property on DataGrid, AutoCompleteBox and ItemsRepeater has been renamed to ItemsSource.

The Items property on MenuFlyout is now readonly - ItemsSource should be used for setting/binding.

Depends on #10827

[timunie]

For the controls which now have only an ItemsSource property, we could add an Items property for compatibility but I've not done that here. Let me know if that would be a good idea.

I personally think the users would expect that if ListBox has a read-only Items property, DataGrid should work similar. So we have a consistent experience over all controls. But I also understand if we want to avoid this overhead. As you said, it can still be added if frequently complaint about.

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0032484-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0033340-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0033348-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]