[UDFS] Fix GCC 13 warnings about uninitialized variables

Also apply _SEH2_VOLATILE where needed (all variables that are set in the __try block and referenced in the __except or __finally block).
It's hard to tell whether these are false positives, because the code is quite a mess.

C:/ReactOS/reactos/drivers/filesystems/udfs/udfinit.cpp: In function 'NTSTATUS UDFDismountDevice(PUNICODE_STRING)':
C:/ReactOS/reactos/drivers/filesystems/udfs/udfinit.cpp:643:36: error: 'Buffer' is used uninitialized [-Werror=uninitialized]
  643 |     PFILE_FS_ATTRIBUTE_INFORMATION Buffer;
      |                                    ^~~~~~

drivers/filesystems/udfs/close.cpp

@@ -1111,7 +1111,7 @@ UDFQueueDelayedClose(
     PtrUDFIrpContextLite    IrpContextLite;
     BOOLEAN                 StartWorker = FALSE;
     _SEH2_VOLATILE BOOLEAN  AcquiredVcb = FALSE;
-    NTSTATUS                RC;
+    _SEH2_VOLATILE NTSTATUS RC = STATUS_UNSUCCESSFUL;
 
     AdPrint(("  UDFQueueDelayedClose\n"));
 

drivers/filesystems/udfs/fileinfo.cpp

@@ -1973,9 +1973,9 @@ UDFRename(
     // Overwite Flag
     BOOLEAN Replace = PtrSp->Parameters.SetFile.ReplaceIfExists &&
                       PtrBuffer->ReplaceIfExists;
-    NTSTATUS RC;
+    _SEH2_VOLATILE NTSTATUS RC = STATUS_UNSUCCESSFUL;
     PVCB Vcb = Fcb1->Vcb;
-    PtrUDFFCB Fcb2;
+    PtrUDFFCB Fcb2 = NULL;
     BOOLEAN ic;
     BOOLEAN AcquiredVcb = TRUE;
     BOOLEAN AcquiredVcbEx = FALSE;
@@ -1985,7 +1985,7 @@ UDFRename(
     BOOLEAN UseClose;
 
     PUDF_FILE_INFO File1;
-    PUDF_FILE_INFO Dir1;
+    _SEH2_VOLATILE PUDF_FILE_INFO Dir1 = NULL;
     PUDF_FILE_INFO Dir2;
     PUDF_FILE_INFO NextFileInfo, fi;
 

drivers/filesystems/udfs/udfinit.cpp

@@ -640,7 +640,7 @@ UDFDismountDevice(
     HANDLE NtFileHandle = (HANDLE)-1;
     OBJECT_ATTRIBUTES ObjectAttributes;
     NOTIFY_MEDIA_CHANGE_USER_IN buffer = { 0 };
-    PFILE_FS_ATTRIBUTE_INFORMATION Buffer;
+    _SEH2_VOLATILE PFILE_FS_ATTRIBUTE_INFORMATION Buffer = NULL;
 
     _SEH2_TRY {