Casting down in TPH should filter by the discriminator when accessing properties mapped to shared columns

In TPH, it's possible to map properties from different siblings in the hierarchy to the same database column. In this scenario, when the base class is cast down in a query and a property is accessed, we'd missing a check on the discriminator, meaning that we'd erroneously return instances of the sibling as well.

C#:

```c#
_ = await ctx.Blogs.Where(b => ((SpecialBlog1)b).Foo == "something").ToListAsync();

public class BlogContext : DbContext
{
public DbSet Blogs { get; set; }

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
=> optionsBuilder
.UseSqlServer(@"Server=localhost;Database=test;User=SA;Password=Abcd5678;Connect Timeout=60;ConnectRetryCount=0;Encrypt=false")
.LogTo(Console.WriteLine, LogLevel.Information)
.EnableSensitiveDataLogging();

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity();
modelBuilder.Entity();
}
}

public class Blog
{
public int Id { get; set; }
}

public class SpecialBlog1 : Blog
{
[Column("Shared")]
public required string Foo { get; set; }
}

public class SpecialBlog2 : Blog
{
[Column("Shared")]
public required string Bar { get; set; }
}
```

Resulting SQL:

```sql
SELECT [b].[Id], [b].[Discriminator], [b].[Shared]
FROM [Blogs] AS [b]
WHERE [b].[Shared] = N'something'
```

This also returns instances of SpecialBlog2. It seems like the WHERE clause should contain a condition for the discriminator.