Renamed auto-data attributes

[aivascu]

Renamed auto-data attributes to match TUnit semantics.

Description

• Renamed ArgumentsAutoDataAttribute to AutoArgumentsAttribute
• Renamed ClassAutoDataAttribute to AutoClassDataSourceAttribute
• Renamed AutoFixtureDataSourceAttribute to AutoDataSourceAttribute
• Renamed MemberAutoDataAttribute to AutoMemberDataSourceAttribute
• Renamed CompositeDataAttribute to CompositeDataSourceAttribute
• Renamed attribute base type
• Removed unused types
• Removed redundant icon images
• Removed leftover xUnit 3 mentions
• Refactored for clarity

Closed issues

Checklist

• Reviewed the contribution guidelines
• Linked the issue(s) the PR closes
• Implemented automated tests and checked coverage
• Provided inline documentation comments for new public API
• Ran the full solution build and validation locally