Fix benchmarks filters

Summary:

The bug was introduced in PR17781
before this fix ./src/bench/bitcoin-bench -filter="RIPEMD160|SHA256|SHA1" will fail with:

# Benchmark, evals, iterations, total, min, max, median
bench_bitcoin: bench/bench.cpp:119: static void benchmark::BenchRunner::RunAll(benchmark::Printer&, uint64_t, double, const string&, bool): Assertion `g_testing_setup == nullptr' failed.
Aborted (core dumped)

This is a backport of Core PR18013

Test Plan: ninja && ./src/bench/bitcoin-bench -filter="RIPEMD160|SHA256|SHA1"

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8690