gdb: Improve stepping

In the Ryujinx GDB stub, when using single stepping (si) in GDB, it cannot correctly step into bl, br, or blr instructions.

To work around this, the ExecuteBranchInstructionForStepping function was previously added to parse these instructions and manually step into them. While it worked, this "hack" was not very clean.

This commit attempt to fixes the stepping behavior in a cleaner way by modifying EmitCall, EmitVirtualCall, and EmitVirtualJump inside the JIT, and removes ExecuteBranchInstructionForStepping.

I am not very familiar with the JIT, so this fix could be incorrect. Please feel free to improve or close this MR if needed.