ci, refactor: Rename VCPKG_TAG variable and vcpkg_cache script
ci, refactor: Rename VCPKG_TAG variable and vcpkg_cache script

The VCPKG_TAG variable renamed to CI_VCPKG_TAG to prevent any possible
name clash with vcpkg-specific variables.

The vcpkg_cache script renamed into more meaningful one.

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