[ecash-herald] Parse token ids for slp2

Summary:
Add more detailed parsing for SLP2 txs

• Had to upgrade ecash-script to get swapEndianness function
• Wrote getSlpTwoToken script to manually parse token genesis info as this is not yet indexed
• Added caching file for token info, can expand this to include common slp v1 or other tokens. Helpful for other tokens but necessary here as the chronik call won't get slp2 genesis info.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14304