util: remove unwanted fields from bitcoin-cli -getinfo

Summary:

In accordance with #17314, Removing noisy fields from -getinfo. Fields removed: protocolversion, walletversion and keypoololdest. In addition to changing bitcoin-cli -getinfo, there is another change to test/functional/interface_bitcoin_cli.py. This change deletes tests that utilize removed -getinfo calls.

Add a release note about this and also about new fields introduced in D8220/PR17302. This is extracted from Core release-notes-0.20.0.md

This is a backport of Core PR17650

Test Plan:
src/bitcoin-cli -getinfo

test/functional/test_runner.py interface_bitcoin_cli.py

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8300