Revert #16058 for non-applicable settings

[kjac]

Prerequisites

• I have added steps to test this contribution in the description below

Description

#16058 had the unintended side effect of breaking a few of our configurations:

• The LoginRedirectUrls and LogoutRedirectUrls of DeliveryApiSettings.MemberAuthorization.AuthorizationCodeFlow.
• The UserDefinedCharCollection of RequestHandlerSettings.

For some reason, it seems that IOptions won't parse an ISet<T> unless T is a simple type like string. The affected configuration collections will simply remain empty, no matter what's in appsettings.json.

This fixes it up by replacing ISet<T> with IEnumerable<T>.

Testing this PR

The easiest way to test this is to add the affected configuration to appsettings.json, then create a custom controller that outputs the configuration. Something like this:

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;
using Umbraco.Cms.Core.Configuration.Models;

namespace Umbraco.Cms.Web.UI.Custom;

[ApiController]
public class MyTestController : ControllerBase
{
    private readonly RequestHandlerSettings _requestHandlerSettings;
    private readonly DeliveryApiSettings _deliveryApiSettings;

    public MyTestController(IOptions<RequestHandlerSettings> requestHandlerSettings, IOptions<DeliveryApiSettings> deliveryApiSettings)
    {
        _requestHandlerSettings = requestHandlerSettings.Value;
        _deliveryApiSettings = deliveryApiSettings.Value;
    }

    [HttpGet("my/test")]
    public IActionResult Get() => Ok(new
    {
        RequestHandlerSettings = _requestHandlerSettings,
        DeliveryApiSettings = _deliveryApiSettings
    });
}

[AndyButland]

Looks good and tests out as expected.