test: Use test_bitcoin setup in bench

Summary:

Now that the fuzz tests can use the BasicTestingSetup [1], do the same
for bench.

Partial backport of core PR15788:
https://github.com/bitcoin/bitcoin/pull/15788/commits/fa8685d49ed8e52b1220a89f669dac63bef172bc

This is stripped down to using the test fixture for the benchmark, as we
have no use for the utils for now.

Depends on D5484.

Test Plan:

make
make check
./src/bench/bench_bitcoin

ninja
ninja check
ninja bench-bitcoin

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5493