E3S8A: Make Argan turn around to face Elyssa at the end of the first memory
E3S8A: Implement cave/hive ambience sounds, SFX fade-out sequences included

Also included are strategically-placed workarounds for the sound source
leakage bug (mainline bug #21426).
E3S8A: Rearrange sound and visual actions at the point the Gatekeeper is slain
E3S8A: Rearrange order of actions at the end of the second meeting cutscene