IPC - Refactor Bcat service to use new ipc - Revisit (#4803)

* bcat ipc

* fix hipc buffer flags

* add buffer fixed size flag on generator

src/Ryujinx.Horizon/Sdk/Bcat/IDeliveryCacheFileService.cs

@@ -0,0 +1,15 @@
+using LibHac.Bcat;
+using Ryujinx.Horizon.Common;
+using Ryujinx.Horizon.Sdk.Sf;
+using System;
+
+namespace Ryujinx.Horizon.Sdk.Bcat
+{
+    internal interface IDeliveryCacheFileService : IServiceObject
+    {
+        Result GetDigest(out Digest digest);
+        Result GetSize(out long size);
+        Result Open(DirectoryName directoryName, FileName fileName);
+        Result Read(long offset, out long bytesRead, Span<byte> data);
+    }
+}