[Feature] Components V2 (#3065)

* oh well. at least it runs

* well that's some breakings

* all the models (i think)

* barebones builder impl

* commit

* initial take on `WithX` component builder design

* actually usable stuff now

* few more changes

* fixes, changes, syntax sugar

* rework message flags + auto add `ComponentsV2`

* apparently it's also nullable

* fix build

* webhook component supports + builder validations + some xmldoc

* `ResolvedUnfurledMediaItem` + fix missing accessory on sections

* missing xmldoc

* fix modal + whatever change

* yeet unused dep

src/Discord.Net.Rest/API/Common/SectionComponent.cs

@@ -0,0 +1,32 @@
+using Discord.Rest;
+using Newtonsoft.Json;
+using System.Linq;
+
+namespace Discord.API;
+
+internal class SectionComponent : IMessageComponent
+{
+    [JsonProperty("type")]
+    public ComponentType Type { get; set; }
+
+    [JsonProperty("id")]
+    public Optional<int> Id { get; set; }
+
+    [JsonProperty("components")]
+    public IMessageComponent[] Components { get; set; }
+
+    [JsonProperty("accessory")]
+    public IMessageComponent Accessory { get; set; }
+
+    public SectionComponent() { }
+
+    public SectionComponent(Discord.SectionComponent component)
+    {
+        Type = component.Type;
+        Id = component.Id ?? Optional<int>.Unspecified;
+        Components = component.Components.Select(x => x.ToModel()).ToArray();
+        Accessory = component.Accessory.ToModel();
+    }
+
+    int? IMessageComponent.Id => Id.ToNullable();
+}