contrib: refactor: simplify block header string routine in linearize-data.py
contrib: refactor: simplify block header string routine in linearize-data.py

The string representation of a block header hash is simply the
hexlified byte-reversed double SHA256 hash of its serialization.

ajtowns/bitcoin,sstone/bitcoin,Xekyo/bitcoin,kallewoof/bitcoin,jlopp/statoshi,Xekyo/bitcoin,namecoin/namecore,jambolo/bitcoin,jambolo/bitcoin,Xekyo/bitcoin,mruddy/bitcoin,AkioNak/bitcoin,namecoin/namecoin-core,bitcoin/bitcoin,kallewoof/bitcoin,domob1812/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,GroestlCoin/GroestlCoin,ajtowns/bitcoin,achow101/bitcoin,GroestlCoin/GroestlCoin,instagibbs/bitcoin,mruddy/bitcoin,anditto/bitcoin,anditto/bitcoin,Xekyo/bitcoin,fujicoin/fujicoin,tecnovert/particl-core,jlopp/statoshi,jambolo/bitcoin,GroestlCoin/bitcoin,tecnovert/particl-core,kallewoof/bitcoin,tecnovert/particl-core,bitcoinsSG/bitcoin,namecoin/namecore,andreaskern/bitcoin,achow101/bitcoin,jamesob/bitcoin,instagibbs/bitcoin,jamesob/bitcoin,fanquake/bitcoin,GroestlCoin/GroestlCoin,bitcoin/bitcoin,jambolo/bitcoin,particl/particl-core,bitcoin/bitcoin,namecoin/namecoin-core,ajtowns/bitcoin,mruddy/bitcoin,fujicoin/fujicoin,GroestlCoin/bitcoin,kallewoof/bitcoin,fanquake/bitcoin,sstone/bitcoin,andreaskern/bitcoin,namecoin/namecoin-core,achow101/bitcoin,tecnovert/particl-core,domob1812/bitcoin,dscotese/bitcoin,particl/particl-core,namecoin/namecore,andreaskern/bitcoin,bitcoinsSG/bitcoin,jambolo/bitcoin,fujicoin/fujicoin,jlopp/statoshi,bitcoinsSG/bitcoin,fujicoin/fujicoin,mruddy/bitcoin,ajtowns/bitcoin,jambolo/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,mruddy/bitcoin,sstone/bitcoin,jlopp/statoshi,instagibbs/bitcoin,instagibbs/bitcoin,AkioNak/bitcoin,dscotese/bitcoin,jamesob/bitcoin,jamesob/bitcoin,particl/particl-core,jlopp/statoshi,GroestlCoin/bitcoin,dscotese/bitcoin,particl/particl-core,ajtowns/bitcoin,bitcoinsSG/bitcoin,kallewoof/bitcoin,sstone/bitcoin,achow101/bitcoin,anditto/bitcoin,lateminer/bitcoin,fujicoin/fujicoin,anditto/bitcoin,GroestlCoin/GroestlCoin,GroestlCoin/bitcoin,sstone/bitcoin,fanquake/bitcoin,tecnovert/particl-core,dscotese/bitcoin,AkioNak/bitcoin,AkioNak/bitcoin,GroestlCoin/bitcoin,particl/particl-core,domob1812/bitcoin,fanquake/bitcoin,anditto/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,lateminer/bitcoin,instagibbs/bitcoin,jamesob/bitcoin,GroestlCoin/bitcoin,namecoin/namecore,sipsorcery/bitcoin,GroestlCoin/GroestlCoin,bitcoin/bitcoin,AkioNak/bitcoin,jamesob/bitcoin,fanquake/bitcoin,namecoin/namecore,namecoin/namecore,GroestlCoin/GroestlCoin,tecnovert/particl-core,dscotese/bitcoin,sipsorcery/bitcoin,domob1812/bitcoin,namecoin/namecoin-core,AkioNak/bitcoin,dscotese/bitcoin,mruddy/bitcoin,bitcoin/bitcoin,anditto/bitcoin,andreaskern/bitcoin,bitcoinsSG/bitcoin,achow101/bitcoin,bitcoin/bitcoin,ajtowns/bitcoin,andreaskern/bitcoin,domob1812/bitcoin,namecoin/namecoin-core,Xekyo/bitcoin,sstone/bitcoin,jlopp/statoshi,lateminer/bitcoin,namecoin/namecoin-core,achow101/bitcoin,sipsorcery/bitcoin,fanquake/bitcoin,fujicoin/fujicoin,particl/particl-core,domob1812/bitcoin,andreaskern/bitcoin,instagibbs/bitcoin,Xekyo/bitcoin,bitcoinsSG/bitcoin