[UDFS] Remove X86 optimizations

[Copilot]

The UDFS driver contained several #ifdef _X86_ code paths using MSVC inline assembly (__asm) as architecture-specific "optimizations", making the code non-portable and incompatible with non-MSVC compilers (e.g. Clang/GCC).

Changes

• udf_info/udf_info.cpp — Drop 256-entry int8 lookup table for valid_char_arr guarded by #ifdef _X86_; use the existing generic string form unconditionally
• udf_dbg.h — Replace __asm int 3 in UDFBreakPoint() with DbgBreakPoint(); collapse dual UDFTouch() implementations into a single portable one using volatile UCHAR to prevent the memory read from being elided
• Include/mem_tools.cpp — Same volatile UCHAR fix for DbgTouch(), removing x86 inline asm variant
• Include/string_lib.cpp — Remove x86 asm string-length loops in RtlAppendUnicodeToString() and MyInitUnicodeString(); keep the generic while(Str2[i]) loop
• Include/mem_tools.h — Replace __asm int 3 debug breakpoints with portable __debugbreak() in MyFreePool__() and MyReallocPool__()

Before (example):

#if defined(_X86_) && defined(_MSC_VER)
__inline VOID UDFTouch(IN PVOID addr) {
    __asm { mov eax,addr; mov al,[byte ptr eax] }
}
#else
__inline VOID UDFTouch(IN PVOID addr) {
    UCHAR a = ((PUCHAR)addr)[0]; a = a;
}
#endif

After:

__inline VOID UDFTouch(IN PVOID addr) {
    volatile UCHAR a = ((PUCHAR)addr)[0];
    (void)a;
}