Scheduler equivalent to `ByType` but for `@multiagent` models.

[Datseris]

see https://discourse.julialang.org/t/agents-jl-v6-releases-announcement-post/111678/6?u=datseris would be nice to have a convenience scheduler that checks the internal property type (is it called type @Tortar ?)

[Datseris]

labelling as QoL as at the moment we can avhieve this with ByProperty.