EntitySplittingMissingPropertiesMainFragment does not take owned navigations/complex properties into account

We have a model validation check to make sure that the main table has at least one non-key property on it (EntitySplittingMissingPropertiesMainFragment). This only looks at regular properties, and does not take owned navigations/complex properties into account. When these are mapped to column(s) on the main table, the check should not throw.

Minimal repro

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

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(b =>
{
b.OwnsMany(p => p.Addresses, b => b.ToJson());
b.SplitToTable("Phonenumbers", b => b.Property(p => p.Phonenumber));
});
}
}

public class Blog
{
public int Id { get; set; }
// public string Name { get; set; } // Without this model validation throws although Addresses is mapped
public string Phonenumber { get; set; }

public List