[HL2MP] Use class-specific swap instead of global V_swap

[speedvoltage]

Issue: The V_swap function faced a problem where it struggled to swap values of different types or handle edge cases, which could cause issues down the road. This might result in incorrect data swaps, causing errors or instability in operations that depend on this function.

Fix: The implementation has been updated to guarantee proper swapping behavior. This involves improving the way values are exchanged to better manage various cases, preventing incorrect memory handling, and ensuring that the swap operation works reliably in all anticipated situations.