refactor: move framerate swim boat hooks

[MohabCodeX]

Summary

This PR addresses the TODO to move frame-rate dependent hooks from CMultiplayerSA.cpp to CMultiplayerSA_FrameRateFixes.cpp, keeping all framerate-related physics corrections consolidated in one place.

Testing

• Tested ped swimming speed in water across 30 FPS and 100 FPS (verified speed and resistance are consistent).
• Tested boat water drag/deceleration at 30 FPS and 100 FPS to ensure physics behavior remains unchanged.

Checklist

• Your code should follow the coding guidelines.
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