Use new `camlist` fields for additional video stream overlay icons.

[bp2008]

JSON camlist new fields:

triggerSource:x
triggerZones:x

#define TRIGGER_SOURCE_MOTION   (1<<1)
#define TRIGGER_SOURCE_ONVIF    (1<<2)
#define TRIGGER_SOURCE_AUDIO    (1<<3)
#define TRIGGER_SOURCE_EXTERNAL (1<<4)
#define TRIGGER_SOURCE_DIO      (1<<5)
#define TRIGGER_SOURCE_GROUP    (1<<6)
#define TRIGGER_SOURCE_CANCELLED (1<<7)
#define TRIGGER_SOURCE_NOSIGNAL (1<<8)

Considerations:

• No system exists currently for per-camera overlays on a group stream.
• camlist update rate may be insufficient

[bp2008]

Added in UI3-133