[WIP] Basic ALP Encoder (not ready for review)

[alamb]

• Stacked on Refactor: Pull common header structures into common module #3

This is part of the ALP encoding work

• part of [Parquet] Prototype ALP encoding apache/arrow-rs#8748
  It targets this PR from @sdf-jkl and @devanbenz
• [WIp] ALP encoder/decoder support apache/arrow-rs#9372

This PR puts in place a basic ALP encoder (it is as small as I can make it).

Currrently the encoder encodes all values as excpetions, which is allowed in the spec, but has worse compression than plain encoding 😆

I basically plan at least two more PRs after this one:

1. implement the FOR encoding
2. Implement sampling to determine factor/scale

Todos:

• Implement variable Vector sizes (currently uses hard coded 2>>11)
• Implement sampling, etc for encoding parameters

[alamb]

An update:

1. I wired in the ALP decoder instantiation so I can make it for either f32 or f64 (can be its own PR)
2. I an currently stuck in trait hell trying to make the code compile, but will get it soon

[alamb]

I hit a snag while trying to be all fancy with a streaming encodr -- which is you don't know up front how many vectors we'll have. I have some ideas about this that I will work on