[Cashtab] [Chronik] [Tx Gen] generateTokenTxOutput - part 1 token genesis tx

Summary:
See T2503 for the pseudocode behind the generateTokenTxOutput function and how it'll be used by overarching token functions.

Part 1 caters for the genesis token tx where the relevant OP_RETURN script and token/xec outputs are added to the transaction builder.

Subsequent diff in this stack will cover the SEND/BURN OP_RETURN scripts and the additional outputs for token send/burn and token change.

Test Plan: npm test and ensure the genesis unit test passes

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12111