Fix simPause for Car

[rajat2004]

Fixes: #4174

About

Fixes the simPause API for Car by using UGamePlayStatistics::SetGamePaused (probably missed in #2292). And some refactoring

How Has This Been Tested?

Using the script given in #4174 (thanks to @suresh-guttikonda!) -
Before fix using 1.6.0 release -

Connected!
Client Ver:1 (Min Req: 1), Server Ver:1 (Min Req: 1)

Before pause: -1.5656204223632812, 0.7037484645843506, 0.998582124710083
After pause: -1.824690818786621, 0.8202106952667236, 0.9985887110233307

After fix -

Connected!
Client Ver:1 (Min Req: 1), Server Ver:1 (Min Req: 1)

Before pause position: <Vector3r> {   'x_val': -8.31222915649414,
    'y_val': -0.0024077333509922028,
    'z_val': 0.2384161353111267}
Before pause diff: -1.7417960166931152, -0.00044455076567828655, 0.9980698227882385
After pause position: <Vector3r> {   'x_val': -8.31222915649414,
    'y_val': -0.0024077333509922028,
    'z_val': 0.2384161353111267}
After pause: -1.7417960166931152, -0.00044455076567828655, 0.9980698227882385

Screenshots (if appropriate):

[zimmy87]

Tested this locally and it works for me, so I am merging this. Thanks for the contribution @rajat2004!