[tg bot] add function returnAddressPreview

Summary:
T2972

Depends on D13362

Add helper function to convert an address string to an abbreviated preview for Telegram msgs. Unit tests specified to reflect customizability if settings change.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D13363