Horizon: Implement arp:r and arp:w services (#5802)

* Horizon: Implement arp:r and arp:w services

* Fix formatting

* Remove HLE arp services

* Revert "Remove HLE arp services"

This reverts commit c576fcccadb963db56b96bacabd1c1ac7abfb1ab.

* Keep LibHac impl since it's used in bcat

* Addresses gdkchan's feedback

* ArpApi in PrepoIpcServer and remove LmApi

* Fix 2

* Fixes ArpApi init

* Fix encoding

* Update PrepoService.cs

* Fix prepo

src/Ryujinx.Horizon/Arp/ArpMain.cs

@@ -0,0 +1,20 @@
+namespace Ryujinx.Horizon.Arp
+{
+    class ArpMain : IService
+    {
+        public static void Main(ServiceTable serviceTable)
+        {
+            ArpIpcServer arpIpcServer = new();
+
+            arpIpcServer.Initialize();
+
+            serviceTable.ArpReader = arpIpcServer.Reader;
+            serviceTable.ArpWriter = arpIpcServer.Writer;
+
+            serviceTable.SignalServiceReady();
+
+            arpIpcServer.ServiceRequests();
+            arpIpcServer.Shutdown();
+        }
+    }
+}