Should the underlying Arraytype be preserved during KeepIndex subsetting?

Currently, KeepIndex subsetting on a ComponentVector based on LabelledVector or OffsetArray returns a ComponenVector based on plain Vector.

using OffsetArrays, LabelledArrays
oaca = ComponentArray(OffsetArray(collect(1:5), -1), Axis(a = 0, b=1:2, c=3, d=4))
oaca[KeepIndex(:b)] |> typeof # does not preserve underlying OffsetArray

na = SLVector(a1=1.1, a2=2.2, a3=3.3)
cv = ComponentVector(na, Axis(:b1,:b2,:b3))
cv[KeepIndex(:b2)] |> typeof # does not preserve underlying AbstractArray

Contrary, it does preserve the type for NamedArrays.

    na = NamedArray(1:3, ([:a1,:a2,:a3],))
    cv = ComponentVector(na, Axis(:b1,:b2,:b3))
    c2 = cv[KeepIndex(:b2)]
    @test getdata(c2)[:a2] == 2

When should the underlying AbstractArray type be preserved and when not?

Start by reproducing the KeepIndex subsetting examples for OffsetArray, LabelledVector, and NamedArray, comparing the resulting ComponentVector and getdata types. Read the KeepIndex and ComponentVector subsetting paths to determine which underlying AbstractArray types are expected to survive. Done means the preservation rule is explicit and the affected examples have matching tests.