Make Changes Activity Logging Text file to JSON file

[MrAk47Anand007]

Update to .NET Framework 4.8 and JSON support

• Updated the target framework version from .NET Framework 4.6 to 4.8 for DigitalWellbeing.Core, DigitalWellbeingService.NET4.6, and DigitalWellbeingWPF. This includes updates in .csproj and App.config files.
• Added Newtonsoft.Json package (v13.0.3) to DigitalWellbeingService.NET4.6 and DigitalWellbeingWPF for enhanced JSON serialization/deserialization.
• Refactored ActivityLogger.cs with new JSON serialization logic, autorun file creation, and usage entry updates.
• Adjusted App.config files across projects for the new framework version and improved XML formatting.
• Updated GeneratedCodeAttribute versions in Resources.Designer.cs and Settings.Designer.cs to reflect newer development tool usage.
• Introduced packages.config files for explicit NuGet package management, specifically adding Newtonsoft.Json.