Performance improvement: Introduce different default bounce numbers per scene

[Azralee]

This branch introduces variable bounce numbers for different scenes. In nearly all scenes the amount of bounces can be reduced to 8 (or even lower), without a noticeable visual impact. Scene 3 is the only one having a lower bound of 16 Bounces.

This significantly improves performance (FPS measured on an RX 6800 (1440p, 8 Samples)):

Number of Bounces	Scene 1	Scene 2	Scene 3	Scene 4	Scene 5
8/8/16/8/8 Bounces (Proposed Default)	45.6	45.2	17.6	51.8	18.4
16 Bounces (Current Default)	38.2	37.7	17.6	29.2	10.5

Images for Comparison: Scene 1: 8 Bounces: 16 Bounces:

Scene 3 (The visual artifacts can be seen on the glass wings): 8 Bounces: 12 Bounces: 16 Bounces:

Scene 5; 8 Bounces: 16 Bounces:

[Azralee]

I'd suggest a squash merge to get rid of the merge commit.