Test on dimnames for KeyedArrays

[glennmoy]

Closes #20

I'll note that #20 describes the situation before we deprecated both eachslice (#15) and mapslices (#45) in the parent apply methods. So the problem it is describing is outdated since we no longer need to take the complement set of dimensions for any transformations.

Still it is important that we support dimnames since user feedback suggested "Not having named dims limits the usefulness of using a KeyedArray as opposed to just an AbstractArray". Fortunately, we already support this, this PR is just making that explicit via the tests.

However

• You can't pass in the keys as inds (for now, we might support this in future)
• This doesn't work with AxisArrays, at least not without AxisArrays first supporting selectdim. Considering we failed to get mapslices into AxisArrays I'm not in a rush to support it as we'll be dropping it internally altogether soon enough.

[codecov]

Codecov Report

Merging #62 (6f67563) into main (ab6ab74) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #62   +/-   ##
=======================================
  Coverage   99.04%   99.04%           
=======================================
  Files          10       10           
  Lines         105      105           
=======================================
  Hits          104      104           
  Misses          1        1           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ab6ab74...6f67563. Read the comment docs.

[bencottier]

Looks good to me