[android/fs] external content loader + nca/xci patches (#3596)

Foreword: WHY DON'T EVERYBODY USE ONE FOLDER FOR EACH GAME+CONTENTS? AIN'T THIS THE FORMAT GAMES COME WHEN YOU BUE THEM? DO YOU LIVE WITH ALL YOUR FRIENDS AND HAVE A 2ND HOUSE FOR ALL THE CHILDREN?

Nice, i feel better now.

This feat extends Maufeat's work on external content loading. It harmonically additions:
"...also, if in each game folder X, you find a folder Y, and in this folder Y you detect ONLY a single game, then mount all external content for that game found in that folder Y and its subfolders."
Permanent (not toggleable). External Content folders are supported equally.

Also:
-Reworked several routines for preserving single source of truth between android and other systems;
-Fixed the annoying unknown format error for content files, by providing proper format detection.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3596
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Co-authored-by: xbzk <xbzk@eden-emu.dev>
Co-committed-by: xbzk <xbzk@eden-emu.dev>

src/core/loader/xci.cpp

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -44,10 +47,13 @@ AppLoader_XCI::~AppLoader_XCI() = default;
 FileType AppLoader_XCI::IdentifyType(const FileSys::VirtualFile& xci_file) {
     const FileSys::XCI xci(xci_file);
 
-    if (xci.GetStatus() == ResultStatus::Success &&
-        xci.GetNCAByType(FileSys::NCAContentType::Program) != nullptr &&
-        AppLoader_NCA::IdentifyType(xci.GetNCAFileByType(FileSys::NCAContentType::Program)) ==
-            FileType::NCA) {
+    if (xci.GetStatus() != ResultStatus::Success) {
+        return FileType::Error;
+    }
+
+    // Identify XCI as a valid container even when it does not include a bootable Program NCA.
+    // Bootability is handled by AppLoader_XCI::Load().
+    if (xci.GetSecurePartitionNSP() != nullptr) {
         return FileType::XCI;
     }