Particle systems which stop playing outside the camera's frustum still return true for IsAlive and isPlaying.

Repro steps:
1. Open TestScene from attached project.
2. If it's not already, set the Particle System position in the scene to 0,0,0.
3. Press Play
4. Observe in the console that the particles are returning true for IsAlive and isPlaying.
5. Wait 6 seconds.
6. Observe that even though there are no more active particles, the system is still returning true for IsAlive and isPlaying.

Expected outcome: Particle System to return false once it stops playing.

Notes:
- I've put down the min distance (14) for the particle system to be outside the camera's frustum. If it's not enough, you can increase it in the Checker script attached to the Particle System.
- Not a regression; happens in 5.2.4f1, 5.3.1f1, and 5.4.0b18
- Behavior slightly different in 5.4.0b18: particle count remains > 0 (it drops to 0 in 5.2 and 5.3)