Multi-threaded "what i see" node

[adamdbrw]

Is your feature request related to a problem? Please describe.
The whatisee node uses a default, single-threaded executor, but it is meant to process potentially data-heavy callback from different sources, which poses a performance problem.

Describe the solution you'd like
Switch to multi-threaded executor. The mutex is already in place.

Describe alternatives you've considered
Dividing the node into separate responsibilities, but they key principle of the node is to be a funnel for AI (since it can only consume 1 image per given rate, at least currently).

Additional context
The mutex is already there, the primary work with this issue is concurrency analysis and testing.