Add dimension_names key to V3 array_metadata

[jhamman]

The V3 spec included a new array metadata field (dimension_names) to specify the names of the axes corresponding to each dimension in an array. This field should be added to the Array constructor and related utilities.

[tasansal]

@jhamman I'll take a stab at this. Can you elaborate on what the "related utilities" are?

[jhamman]

@tasansal - we may want to hold on this until some internal refactors land on #1290. We are currently exploring the best path to bringing this library up to spec and are considering pulling in some of the internal work sitting in Zarritta. That lib already has the dimension names attribute so if we pull the V3Array class over, this will come for free.

I definitely don't want to wave you off of contributions here though so don't go far! There is lots to do.

[jhamman]

Closing as this is now done on the v3 branch. See #1583 for more context on the v3 effort.

p.s. @tasansal - would be happy to get your 👀 on the above design doc.