Disable logic to add support to `model_boundary`
Disable logic to add support to `model_boundary`

We _do_ want to enable this however there is a bug in the current implementation. It is checking _all_ the extruders and if `travel_avoid_supports` is enabled on one of the extruders then this feature is enabled for all combing.

This introduces problems for PVA support. If `travel_avoid_supports` is disabled for the PLA extruder but disabled for the PVA extruder the `model_boundary` will contain the boundary for support. As there are many travel moves within/through this model boundary with support area's included there will be many retractions. This is the main cause for https://ultimaker.atlassian.net/browse/CURA-9163.

Note that `model_boundary` is only used in a very specific case where combing fails to travel via the outside of the travel-avoid distance (see https://github.com/Ultimaker/CuraEngine/pull/1626)

CURA-9163

Ultimaker/CuraEngine,Ultimaker/CuraEngine