unittests: Add a test for constprop size bugs

fails on main, fixed by this PR.

unittests/ASM/FEX_bugs/OptSizeConfusion.asm

@@ -0,0 +1,26 @@
+%ifdef CONFIG
+{
+  "RegData": {
+    "RAX": "0x000000000f0f0f0f",
+    "RBX": "0x000000000f0f0f0f",
+    "RCX": "0x000000000f0f0f0f",
+    "RDX": "0x00000000ffffffff",
+    "R9": "0x000000000f0f0f0f"
+  }
+}
+%endif
+
+; FEX had several bugs in its constprop pass where 32->64 bit truncation behaviour wasn't accounted for leading
+; to incorrectly inserting instead.
+
+mov rax, 0x0f0f0f0f0f0f0f0f
+mov rbx, 0x0f0f0f0f0f0f0f0f
+mov rcx, 0x0f0f0f0f0f0f0f0f
+mov rdx, 1
+mov r9, 0x0f0f0f0f0f0f0f0f
+xor eax, 0
+and ebx, ebx
+shr ecx, 0
+neg edx
+shl r9d, 0
+hlt