bench/rpc_mempool: Create ChainTestingSetup, use its CTxMemPool
bench/rpc_mempool: Create ChainTestingSetup, use its CTxMemPool

This is correct because:

- The ChainTestingSetup is constructed before the call to bench.run(...)
- All the runs are performed on the same mempool

jambolo/bitcoin,namecoin/namecoin-core,ajtowns/bitcoin,kallewoof/bitcoin,sipsorcery/bitcoin,Xekyo/bitcoin,mruddy/bitcoin,fanquake/bitcoin,sstone/bitcoin,mruddy/bitcoin,bitcoin/bitcoin,ajtowns/bitcoin,Xekyo/bitcoin,sipsorcery/bitcoin,jambolo/bitcoin,mruddy/bitcoin,bitcoin/bitcoin,tecnovert/particl-core,namecoin/namecoin-core,kallewoof/bitcoin,jambolo/bitcoin,fujicoin/fujicoin,sipsorcery/bitcoin,AkioNak/bitcoin,jamesob/bitcoin,instagibbs/bitcoin,particl/particl-core,sstone/bitcoin,bitcoinsSG/bitcoin,domob1812/bitcoin,bitcoinsSG/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,namecoin/namecoin-core,bitcoin/bitcoin,tecnovert/particl-core,namecoin/namecore,kallewoof/bitcoin,domob1812/bitcoin,kallewoof/bitcoin,particl/particl-core,namecoin/namecoin-core,jambolo/bitcoin,ajtowns/bitcoin,fujicoin/fujicoin,lateminer/bitcoin,jambolo/bitcoin,ajtowns/bitcoin,ajtowns/bitcoin,jamesob/bitcoin,fanquake/bitcoin,particl/particl-core,Xekyo/bitcoin,instagibbs/bitcoin,kallewoof/bitcoin,tecnovert/particl-core,kallewoof/bitcoin,tecnovert/particl-core,bitcoinsSG/bitcoin,particl/particl-core,namecoin/namecoin-core,jambolo/bitcoin,sstone/bitcoin,AkioNak/bitcoin,AkioNak/bitcoin,domob1812/bitcoin,ajtowns/bitcoin,lateminer/bitcoin,tecnovert/particl-core,domob1812/bitcoin,namecoin/namecore,fanquake/bitcoin,instagibbs/bitcoin,Xekyo/bitcoin,jamesob/bitcoin,mruddy/bitcoin,namecoin/namecoin-core,instagibbs/bitcoin,fujicoin/fujicoin,fanquake/bitcoin,namecoin/namecore,tecnovert/particl-core,jamesob/bitcoin,lateminer/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,instagibbs/bitcoin,instagibbs/bitcoin,fujicoin/fujicoin,Xekyo/bitcoin,AkioNak/bitcoin,lateminer/bitcoin,domob1812/bitcoin,jamesob/bitcoin,bitcoin/bitcoin,namecoin/namecore,namecoin/namecore,bitcoin/bitcoin,fanquake/bitcoin,domob1812/bitcoin,AkioNak/bitcoin,mruddy/bitcoin,fanquake/bitcoin,jamesob/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,bitcoinsSG/bitcoin,sstone/bitcoin,sstone/bitcoin,namecoin/namecore,sstone/bitcoin,mruddy/bitcoin,fujicoin/fujicoin,sipsorcery/bitcoin,bitcoinsSG/bitcoin,fujicoin/fujicoin,particl/particl-core,AkioNak/bitcoin,bitcoin/bitcoin,particl/particl-core