Implement pointer and resize! for VectorOfArray

[ranocha]

This came up in https://github.com/SciML/OrdinaryDiffEq.jl/pull/2087/files and the related PR SciML/SciMLBase.jl#561. It would be great if the following operations were allowed:

julia> using Pkg; Pkg.activate(temp = true); Pkg.add(["StaticArrays", "RecursiveArrayTools"])
[...]
  [731186ca] + RecursiveArrayTools v3.0.0
  [90137ffa] + StaticArrays v1.7.0
[...]

julia> using StaticArrays, RecursiveArrayTools

julia> u = VectorOfArray(ones(SVector{2, Float64}))
VectorOfArray{Float64,1}:
2-element SVector{2, Float64} with indices SOneTo(2):
 1.0
 1.0

julia> resize!(u, 5)
ERROR: MethodError: no method matching resize!(::VectorOfArray{Float64, 1, SVector{2, Float64}}, ::Int64)
[...]

julia> pointer(u)
ERROR: MethodError: no method matching pointer(::VectorOfArray{Float64, 1, SVector{2, Float64}})
[...]