[file_sys] robust-er IPSwitch compiler (#3911)

this PR reworks IPS parser to be less stupid
what do i mean by this? well generally give it a bit of
love so it doesn't do a lot of unsound allocations
also simplify the logic greatly (and use memcmp() string idiom
instead of trusting the compiler so blindly...)

no this doesn't mean to uber optimize IPS to handle 999 gb/s
it's more so it doesn't outright crash with edge cases
as the previous codebase was quite spaghetty

also the major overhead is obviously the vector shenanigans
and the I/O -- but thats out of scope

Test that IPSwitch mods still properly work WITH ANY GAME
IF THERE IS ANY REGRESSION IN SOME GAME/MOD THEN
TELL ME

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3911
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

src/core/file_sys/ips_layer.h

@@ -1,11 +1,14 @@
+// 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
 
 #pragma once
 
 #include <array>
-#include <memory>
 #include <vector>
+#include <span>
 
 #include "common/common_types.h"
 #include "core/file_sys/vfs/vfs.h"
@@ -20,24 +23,17 @@ public:
     ~IPSwitchCompiler();
 
     std::array<u8, 0x20> GetBuildID() const;
-    bool IsValid() const;
     VirtualFile Apply(const VirtualFile& in) const;
 
 private:
     struct IPSwitchPatch;
 
     void ParseFlag(const std::string& flag);
-    void Parse();
-
-    bool valid = false;
+    void Parse(std::span<u8 const> bytes);
 
     VirtualFile patch_text;
     std::vector<IPSwitchPatch> patches;
     std::array<u8, 0x20> nso_build_id{};
-    bool is_little_endian = false;
-    s64 offset_shift = 0;
-    bool print_values = false;
-    std::string last_comment = "";
 };
 
 } // namespace FileSys