rangebars() does not honor convert_single_argument override

[staticfloat]

• are you running newest version (version from docs) ? (WGLMakie v0.9.7)
• can you reproduce the bug with a fresh environment ? (]activate --temp; add Makie)
• What platform + GPU are you on? (M1 MBP, macOS)

If I have a custom type that I want Makie to be able to peel via convert_single_argument() it works with things like lines(), but not rangebars():

using WGLMakie

struct CustomType
    v::Float64
end

Makie.convert_single_argument(c::CustomType) = c.v
Makie.convert_single_argument(cs::AbstractArray{<:CustomType}) = [c.v for c in cs]

# This works
xs = 1:10
ys = CustomType.(Float64.(1:10))
lines(xs, ys)

# This does not
rangebars(ys, xs .- 1, xs .+ 1)

The above results in:

julia> rangebars(ys, xs .- 1, xs .+ 1)

       # We must manually peel the ys for rangebars:
ERROR: MethodError: Cannot `convert` an object of type CustomType to an object of type Float32
The function `convert` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  convert(::Type{T}, ::Ratios.SimpleRatio{S}) where {T<:AbstractFloat, S}
   @ Ratios ~/.julia/packages/Ratios/FsiCW/src/Ratios.jl:51
  convert(::Type{T}, ::Number) where T<:Number
   @ Base number.jl:7
  convert(::Type{T}, ::Quantity) where T<:Real
   @ Unitful ~/.julia/packages/Unitful/R4J37/src/conversion.jl:139
  ...

Stacktrace:
  [1] macro expansion
    @ ~/.julia/packages/StaticArraysCore/P6PH7/src/StaticArraysCore.jl:88 [inlined]
  [2] convert_ntuple
    @ ~/.julia/packages/StaticArraysCore/P6PH7/src/StaticArraysCore.jl:84 [inlined]
  [3] Vec{3, Float32}(x::Tuple{CustomType, Int64, Int64})
    @ GeometryBasics ~/.julia/packages/GeometryBasics/bLARu/src/fixed_arrays.jl:19
  [4] StaticArray
    @ ~/.julia/packages/StaticArrays/oOCPP/src/convert.jl:165 [inlined]
  [5] _broadcast_getindex_evalf
    @ ./broadcast.jl:673 [inlined]
  [6] _broadcast_getindex
    @ ./broadcast.jl:646 [inlined]
  [7] getindex
    @ ./broadcast.jl:605 [inlined]
  [8] copy
    @ ./broadcast.jl:906 [inlined]
  [9] materialize
    @ ./broadcast.jl:867 [inlined]
 [10] broadcast
    @ ./broadcast.jl:805 [inlined]
 [11] convert_arguments
    @ ~/.julia/packages/Makie/z2T2o/src/basic_recipes/error_and_rangebars.jl:119 [inlined]
 [12] (Plot{Makie.rangebars})(args::Tuple{Vector{…}, UnitRange{…}, UnitRange{…}}, plot_attributes::Dict{Symbol, Any})
    @ Makie ~/.julia/packages/Makie/z2T2o/src/interfaces.jl:139
 [13] _create_plot(::Function, ::Dict{Symbol, Any}, ::Vector{CustomType}, ::Vararg{Any})
    @ Makie ~/.julia/packages/Makie/z2T2o/src/figureplotting.jl:248
 [14] rangebars(::Vector{CustomType}, ::Vararg{Any}; kw::@Kwargs{})
    @ Makie ~/.julia/packages/MakieCore/UAwps/src/recipes.jl:175
 [15] top-level scope
    @ REPL[99]:1
Some type information was truncated. Use `show(err)` to see complete types.

# We must manually peel the ys for rangebars:
rangebars(Makie.convert_single_argument(ys), xs .- 1, xs .+ 1; direction=:x)

[SimonDanisch]

I will take a look at this as part of #3226 ... I think, this happens, because rangebars overloads convert_arguments quite broadly so it doesn't get dispatched to Makie's generic convert_arguments, which is the one that applies convert_single_argument.