I've added a new data provider project, AppCoreNet.Data.EntityFramework, similar to the existing AppCoreNet.Data.EntityFrameworkCore project, but this one uses Entity Framework 6.

Here are the key changes:
- I created the AppCoreNet.Data.EntityFramework project targeting net462.
- I ported and adapted classes from the EF Core provider, including:
    - EntityFrameworkDataProvider
    - EntityFrameworkRepository
    - EntityFrameworkTransactionManager
    - Associated query handlers and helper classes.
- I implemented DbModelProperties.cs using EF6 metadata APIs to determine primary keys and concurrency tokens.
- I implemented dynamic LINQ expression-based primary key querying in EntityFrameworkRepository.ApplyPrimaryKeyExpression.
- I adapted Dependency Injection services for EF6.
- I added the new project to AppCoreNet.Data.sln and Directory.Packages.props.
- I created a basic test project AppCoreNet.Data.EntityFramework.Tests with xUnit and Effort.EF6.

KNOWN ISSUE:
The AppCoreNet.Data.EntityFramework project currently fails to compile due to error CS1061: 'Database' does not contain a definition for 'BeginTransactionAsync' in EntityFrameworkTransactionManager.cs. This issue persists despite correct package references (EntityFramework 6.4.4) and using directives. I suspect it might be an issue with the build environment or .NET Framework SDK targeting that prevents the compiler from discovering the EF6 extension methods. This is currently preventing me from running tests for the EF6 provider.