Required dependent of optional dependent is not materialized/updated properly

An aggregate root has a 1:0..1 optional dependent with some required properties, using table splitting. This dependent entity has a 1:1 required dependent where all properties are nullable (that's why this nav is required). After the optional dependent has saved values, changes on the required dependent entity are not saved.

### Steps to reproduce

Build & run.
Observe the last issued SQL command and "State before save:" line on the console output.
If the required dependent is replaced: "State before save: Added" and an update command.
If the required dependent is reused: "State before save: Detached" and no update command.
(note that both City and Street columns are updated in the former case despite the Street not changing)
```c#
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

// Prep the db & seed
using( var db = new AppDb() )
{
db.Database.EnsureDeleted();
db.Database.EnsureCreated();
db.Parents.Add(new() { Id = "x", Child = new() { Name = "asd" } });
db.SaveChanges();
}

// reproduce the issue
using( var db = new AppDb() )
{
var parent = db.Parents.Single();
// This will update
//parent.Child!.Address = new() { City = "asd" };
// This will not
parent.Child!.Address.City = "asd";
db.ChangeTracker.DetectChanges();
Console.WriteLine($"State before save: {db.Entry(parent.Child.Address).State}");
db.SaveChanges();
}

// Model
class AppDb : DbContext
{
protected override void OnConfiguring(DbContextOptionsBuilder builder)
{
builder
.UseSqlServer("Data Source=localhost;Initial Catalog=Test;Integrated Security=true")
.LogTo(Console.WriteLine, LogLevel.Information)
.EnableSensitiveDataLogging()
;
}
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity().OwnsOne(e => e.Child).OwnsOne(e => e.Address);
}
public DbSet Parents => this.Set();
}

class Parent
{
public required string Id { get; set; }
public Child? Child { get; set; }
}
class Child
{
public required string Name { get; set; }
public Address Address { get; set; } = new();
}
class Address
{
// All optional, hence the navigation to this entity is required
public string? City { get; set; }
public string? Street { get; set; }
}
```

First I thought this has to do with owned entities and thus part of #24581 and #1985 however it repros with plain old navigations. Replace OnModelCreating with the following (basically maps to the same table structure), steps and outcome is the same
```c#
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity().ToTable("Parents");
builder.Entity().HasOne(e => e.Child).WithOne().HasForeignKey();
builder.Entity().Navigation(e => e.Child).AutoInclude();
builder.Entity().Property("Id");
builder.Entity().HasKey("Id");
builder.Entity().ToTable("Parents");
builder.Entity().HasOne(e => e.Address).WithOne().HasForeignKey