LightningJit: Reduce stack usage for Arm32 code (#6245)

* Write/read guest state to context for sync points, stop reserving stack for them

* Fix UsedGprsMask not being updated when allocating with preferencing

* POP should be also considered a return

src/Ryujinx.Cpu/LightningJit/Arm32/RegisterAllocator.cs

@@ -106,6 +106,7 @@ namespace Ryujinx.Cpu.LightningJit.Arm32
                 if ((regMask & AbiConstants.ReservedRegsMask) == 0)
                 {
                     _gprMask |= regMask;
+                    UsedGprsMask |= regMask;
 
                     return firstCalleeSaved;
                 }