Support large arrays

[CurtHagenlocher]

Describe the enhancement requested

It's hard for the C# Arrow library to support large arrays. Commonly-used types like Array, Span and Memory use a 32-bit signed integer for the length, meaning that they can't have more than ~2 million elements in them. The ArrowBuffer structure that is the foundation of the core ArrayData class exposes these types directly. This may make it impossible to support large arrays in a strictly backwards-compatible fashion.

Some previously-opened items related to this feature are:

apache/arrow#23776
apache/arrow#38086
apache/arrow#38619
apache/arrow#45030

[CurtHagenlocher]

Another consideration is that the .NET FlatBuffers library also has a dependency on the same types, so it will likely become necessary to fork FlatBuffers to make this work (q.v. #18)