Fix benchmarks filters

Summary:
> The bug was introduced in [[bitcoin/bitcoin#17781 | 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 [[bitcoin/bitcoin#18013 | 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

src/bench/bench.cpp

@@ -156,6 +156,7 @@ void benchmark::BenchRunner::RunAll(Printer &printer, uint64_t num_evals,
         assert(::ChainActive().Height() == 0);
 
         if (!std::regex_match(p.first, baseMatch, reFilter)) {
+            g_testing_setup = nullptr;
             continue;
         }