Can't include constant GUIDs in the projection

[roji]

When including a constant Guid in a projected, unmapped type (e.g. DTO), EF seems to treat it as text and fails loading.

Minimal repro:

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Blogs.Add(new Blog { Id = Guid.NewGuid() });
await context.SaveChangesAsync();

var query = await context.Blogs
    .Select(a => new BlogVm
    {
        Id = a.Id,
        SomeInt = 8, // This works
        SomeViewModelReference = Guid.Empty, // This fails
    })
    .ToListAsync();

public class BlogContext : DbContext
{
    public DbSet<Blog> 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();
}

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

public class BlogVm
{
    public Guid Id { get; set; }
    public Guid SomeViewModelReference { get; set; }
    public int SomeInt {get; set;}
}

SQL:

SELECT [b].[Id], 8 AS [SomeInt], '00000000-0000-0000-0000-000000000000' AS [SomeViewModelReference]
FROM [Blogs] AS [b]

Exception:

Unhandled exception. System.InvalidCastException: Unable to cast object of type 'System.Guid' to type 'System.String'.
   at Microsoft.Data.SqlClient.SqlBuffer.get_Guid()
   at Microsoft.Data.SqlClient.SqlDataReader.GetGuid(Int32 i)
   at lambda_method23(Closure, QueryContext, DbDataReader, ResultContext, SingleQueryResultCoordinator)
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync() in /Users/roji/projects/efcore/src/EFCore.Relational/Query/Internal/SingleQueryingEnumerable.cs:line 364

Of course, when investigating this check other types as well, as this is likely part of a larger problem.

Originally reported by @espentveit in npgsql/efcore.pg#3507