intersect on DimUnitRanges returns a Base UnitRange

[asinghvi17]

MWE:

julia> import DimensionalData as DD; using DimensionalData

julia> intersect(DD.Dimensions.DimUnitRange(1:5, X()), DD.Dimensions.DimUnitRange(3:7, X()))
3:5

julia> typeof(ans)
UnitRange{Int64}

Ideally this should return a DimUnitRange. Maybe it could also check that dimensions match. Let me know if this makes sense, and I can PR it.

[rafaqz]

Probably makes sense

[asinghvi17]

Also, should dims2indices on an extent return a DimUnitRange?

[rafaqz]

That would mean selectors also returning DimUnitRange.

There's a compilation overhead to doing that.

What would be the benefit?

[rafaqz]

We will need to use promote_dim on the dimensions to get the right type back.

And also check that the lookup values match after the intersection.