[WIP] Parquet Go ALP implementation support

[ArnavBalyan]

cc @julienledem @alamb

Rationale for this change

• Implements ALP (Adaptive Lossless floating point) encoding for float and double columns as per Prateek's spec. Related to GH-533: Adaptive Lossless Floating-Point (ALP) Encoding parquet-format#548.
• ALP converts floating point values to integers via decimal scaling, then applies For and bit packing. Values that don't round trip exactly are stored as exceptions.
• The encoder is incremental and flushes per vector as values arrive. The decoder is lazy with vectors decoded on demand via offset array.

What changes are included in this PR?

• Wired ALP implementation through encoder.go and decoder.go based on the original spec.
• Registered a new encoding as Encodings.ALP.
• Added unit tests/cross compat tests

Are these changes tested?

• Yes new unit tests were added, all of which pass in addition to the existing tests.
• Cross compat tests were added, the external encoded file can be provided as env var which triggers arrow-go ALP decoding.

Are there any user-facing changes?

• Yes