qt: test: Create at most one testing setup
It is assumed that ideally only one BasicTestingSetup exists at any point in time for each process (due to use of globals). This assumption is violated in the GUI tests, as a testing setup is created as the first step of the main function and then (sometimes) another one for the following test cases. So, the gui tests create two testing setups: BasicTestingSetup in main (added in fa4a04a) a testing setup for individual test cases Avoid that by destructing the testing setup in main after creation and then move the explicit ECC_Stop to the only places where it is needed (before and after apptests).
Backport of core PR16294.
Depends on D5556.
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D5557