Indexing OneTo with IdentityUnitRange preserves axes

[jishnub]

On master:

julia> Base.OneTo(10)[Base.IdentityUnitRange(2:7)]
2:7

After this PR:

julia> Base.OneTo(10)[Base.IdentityUnitRange(2:7)]
Base.IdentityUnitRange(2:7)

[johnnychen94]

I understand that this cooperates with #40660 and OffsetArrays for more consistent result:

using OffsetArrays

inds = Base.IdentityUnitRange(2:7);

(1:7)[inds] |> axes
# (OffsetArrays.IdOffsetRange(values=2:7, indices=2:7),)

collect(1:7)[inds] |> axes
# (OffsetArrays.IdOffsetRange(values=2:7, indices=2:7),)

# fixes the inconsistency in master
Base.OneTo(7)[inds] |> axes
# master: (Base.OneTo(6),)
# PR: (Base.IdentityUnitRange(2:7),)