API improvements for Arrow arrays

[CurtHagenlocher]

Describe the enhancement requested

A number of improvements have been suggested over the years to improve the Arrow APIs. Some of these would be backwards-incompatible.

• Implement IEqualityComparer<Schema>
• Implement IEqualityComparer<Field>
• Fix implementation of IEquatable on arrays
• Standardize on a base class instead of an interface
• Add pretty-printing methods
• Define scalar types for all Arrow types

apache/arrow#21197
apache/arrow#21748
apache/arrow#21992
apache/arrow#36777
apache/arrow#45095