Fix DataGrid can't select or edit when rows matches in equality

[ionite34]

What does the pull request do?

Fixes #13894 (When a DataGrid have two or more rows with same content that match the Equals with true against the other element, those can't be selected nor edited.)

What is the current behavior?

DataGrid using DataGridCollectionView as ItemSource with items that implements IEquatable with each other and are equal (e.g. default record objects as blank rows) are not selectable and not editable.

What is the updated/expected behavior with this PR?

DataGrid can now have rows items that implement IEquatable and are equal with other rows without causing edit / selection issues.

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

Changes some previous usages of Object.Equals and == to Object.ReferenceEquals

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

N/A. Since previously the DataGridCollectionView wasn't deduplicating items that are equal, instead allowing them to be added but not be editable or selectable, I doubt anyone is using this as intended behavior.

Obsoletions / Deprecations

N/A.

Fixed issues

Fixes #13894

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0051517-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• All contributors have signed the CLA.

[ionite34]

@cla-avalonia agree

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0051658-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]