[Chronik] Add slp::parse, with support for SLP GENESIS txs

Summary:
Parses SLP txs, and for now we only add support for parsing GENESIS txs.

GENESIS txs create a new token with its own ID, which is the txid of the GENESIS tx.

Depends on D15009 and D15011.

Test Plan: cargo test -p bitcoinsuite-slp

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: osoftware

Differential Revision: https://reviews.bitcoinabc.org/D15012