Fix BlockToJsonVerbose benchmark
Summary:
Currently it was not possible to run just the BlockToJsonVerboes benchmarsk because it did not set up everything it needed, running bench_bitcoin -filter=BlockToJsonVerbose caused this assert to fail:
bench_bitcoin: chainparams.cpp:506: const CChainParams& Params(): Assertion `globalChainParams' failed.
Initializing TestingSetup fixes this.
This is a backport of core#20998
Test Plan:
ninja bench-bitcoin src/bench/bitcoin-bench -filter=BlockToJsonVerbose
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Subscribers: Fabien
Differential Revision: https://reviews.bitcoinabc.org/D13039