[Chronik] Add alp::parse to parse GENESIS, MINT, SEND and BURN

Summary:
Parses a single ALP pushdata. The protocol encoding is simpler than SLP, so we can add the parsing in one diff.

ALP spec can be found here.

Test Plan: cargo test -p bitcoinsuite-slp

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D15024