`fcollect` won't keep repeated arrays that are `==` but distinct

[ericphanson]

See beacon-biosignals/LegolasFlux.jl#4 (comment) and the alternate implementation

function fcollect2(x; output = [], cache = Base.IdSet(), exclude = v -> false)
    x in cache && return output
    if !exclude(x)
      push!(cache, x)
      push!(output, x)
      foreach(y -> fcollect2(y; cache = cache, output=output, exclude = exclude), Functors.children(x))
    end
    return output
end

[DhairyaLGandhi]

A pr would be great with a small mwe from beacon-biosignals/LegolasFlux.jl#4 (comment) @ericphanson !