FEXCore: Removes syscall optimization

The JIT was doing a bunch of additional work where it was saving and
restoring registers and then juggling the arguments back in to a stack
frame. All of this is nonsensical without the optimization where we
could call syscalls inline without a stack frame.

Instead remove this optimization entirely and behave like a "generic"
syscall path always. The Linux syscall handler now pulls the arguments
out of the CPU context directly and stores the result back in to RAX
directly as well.

This has knock-on effects where technically syscalls are
going to be slightly faster because no stack frame setup for the
arguments, but additionally we are going to be able to have syscalls be
proper serialization points where we can interrupt the syscall and
long-jump out without problems.

Bumps the DiskCache version again because it causes codegen to change.

FEXCore/Source/Interface/IR/IR.json

@@ -326,11 +326,10 @@
       "CallbackReturn": {
         "HasSideEffects": true
       },
-      "GPR = Syscall GPR:$SyscallID, GPR:$Arg0, GPR:$Arg1, GPR:$Arg2, GPR:$Arg3, GPR:$Arg4, GPR:$Arg5": {
+      "Syscall": {
         "HasSideEffects": true,
         "Desc": ["Dispatches a guest syscall through to the SyscallHandler class"
-                ],
-        "DestSize": "OpSize::i64Bit"
+                ]
       },
 
       "Thunk GPR:$ArgPtr, SHA256Sum:$ThunkNameHash": {