Implement Array equality

[kylebarron]

Not exactly sure how this should be defined. @d-v-b any ideas?

[d-v-b]

I'd probably define equality between two array handles operationally to mean "writing the same in-memory values through both handles produces the same stored state; reading from the same stored state produces the same in-memory values", so basically same metadata, same runtime configuration, same store, etc. Equality between arrays should not be used to compare chunk values, because that's very expensive.