[common] use abi::__cxa_demangle for demangling using the system's glibcxx/libc++ (#3894)

most stdlibc++ already provide this functionality out of the box, very consistently and well implemented (usually)

my main irk is that the llvm itanium demangle is totally unescesary when there is a perfectly stable, tested and well documented equivalent functionality in the standard stdc++ provided in most UNIX oses

its mostly to reduce binary size by a very thin margin, but he stdc++ is more than capable of doing he same behaviour we use a dpeendency for

for mingw or such howeger,, demangling becomies trickier so we have to exclude windows entirely because well windows likes to do things differently dont they

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3894
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/common/demangle.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later