best_image_timeout per zone and/or object

**Describe what you are trying to accomplish and why in non technical terms**
I want to be able to get best picture depending on zone/object type. E.g. for persons delay up to 60 seconds is Ok but for cars it is usually too high and leads to detections of wrong objects (e.g. parked cars) if they just pass by in a couple of seconds.

**Describe the solution you'd like**
I want to be able to define best_image_timeout per zone and/or object.

**Describe alternatives you've considered**
If I reduce best_image_timeout per camera, I may get a good picture of a car but not very good picture of a person. Tuning person detection is possible but will complicate the configuration and obviously in some cases persons will not be detected.

**Additional context**
My camera is pointed to my front yard, driveway and a road where cars can go 20mph and pass by in 2-3 seconds.

The issue names no files or tests. Start by locating the existing best_image_timeout configuration and the code that selects best images, then determine how zones and object types are represented. Done means the timeout can be configured per zone and/or object without losing the existing camera-level behavior, with coverage for the new configuration.

Written by the indexing model from the issue text.