Identity: `IdentityOptions` should be inside an `IOptionsSnapshot`

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the bug

If the user changes at runtime the `IdentityOptions` the changes are not reflected.

### Expected Behavior

Changed `IdentityOptions` should be reflected.

### Steps To Reproduce

1. Create a simple project `dotnet new mvc --auth Individual`.
2. At `Program.cs`
```cs
builder.Services.AddOptions().BindConfiguration("Identity");
```
2. Create a User
3. Change the `PasswordOptions`. at `appsettings.json` or another configuration source.
4. Try to create another User with the changed options, they are not reflected until another restart.

### Exceptions (if any)

_No response_

### .NET Version

8.0.204

### Anything else?

The cause is this constructor, it should be `IOptionsSnapshot`
https://github.com/dotnet/aspnetcore/blob/b83e1e159ef1bdfe638e36c8b00bc65ed2d1d857/src/Identity/Extensions.Core/src/UserManager.cs#L70