[chronik-client] Support tx and block-txs endpoints in ChronikClientNode

Summary:
Add support for the chronik.tx(txid) and chronik.blockTxs(hashOrHeight, pageNumber, pageSize) endpoints in the in-node version of chronik-client

Convert value key from string to number. Convert timestamp and timeFirstSeen keys from string to number.

Test Plan: teamcity CI tests in this diff, or see local testing approach from test plan at D14915

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15278