[tests] Functional tests call self.start_node(s) and self.stop_node(s)

Summary:
This commit changes the individual test scripts to call the
start_node(s) and stop_node(s) methods in BitcoinTestFramework.

This is the first part of the backport of core's PR10359

Depends on D976, D972, D978, D981 and D983

Test Plan:

make check
./test/functional/test_runner.py --extended

Reviewers: #bitcoin_abc, schancel

Reviewed By: #bitcoin_abc, schancel

Differential Revision: https://reviews.bitcoinabc.org/D982