TestNodeCLI batch emulation

Summary:
Support same get_request and batch methods as AuthServiceProxy

Partial backport of core PR11970 (commit ff9a363)

Depends on D2397

Test Plan:

./test/functional/test_runner.py interface_bitcoin_cli

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2398