[chronik-client] Add block and blocks methods to in-node chronik-client

Summary: Add support for chronik.block() and chronik.blocks() methods to in-node chronik-client, with associated integration testing and support script

Test Plan: CI builds successfully, ref test plan in D14915 to test locally

Reviewers: #bitcoin_abc, PiRK, Fabien

Reviewed By: #bitcoin_abc, PiRK, Fabien

Subscribers: Fabien, PiRK, emack

Differential Revision: https://reviews.bitcoinabc.org/D15210