[CMAKE] Run test/util/bitcoin-util-test.py with ninja check

Summary:
Add a few new rules to cmake:

• bitcoin-util-test will run bitcoin-util-test.py
• check now includes bitcoin-util-test

This mimics the behaviour of make check with autotools

Test Plan:

mkdir buildcmake && cd buildcmake
cmake -GNinja ..
ninja bitcoin-util-test
ninja check

Should return an unknown target error, as bitcoin-tx is required:

cmake -DBUILD_BITCOIN_TX=OFF -GNinja .. && ninja bitcoin-util-test

Should run the tests but not bitcoin-util-test:

cmake -DBUILD_BITCOIN_TX=OFF -GNinja .. && ninja check

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2494