IsInitialBlockDownload no longer uses header-only timestamps.
IsInitialBlockDownload no longer uses header-only timestamps.

This avoids a corner case (mostly visible on testnet) where bogus
 headers can keep nodes in IsInitialBlockDownload.

Github-Pull: #9053
Rebased-From: e141beb6a9816b7e1e680fb0a8bae16d42a3e557

lbrtcoin/albertcoin,gravio-net/graviocoin,HashUnlimited/Einsteinium-Unlimited,Electronic-Gulden-Foundation/egulden,zcoinofficial/zcoin,okinc/bitcoin,litecoin-project/litecore-litecoin,oklink-dev/bitcoin,HashUnlimited/Einsteinium-Unlimited,EntropyFactory/creativechain-core,cannabiscoindev/cannabiscoin420,zetacoin/zetacoin,bitcoinplusorg/xbcwalletsource,funkshelper/woodcore,bitcoinplusorg/xbcwalletsource,jl2012/litecoin,OmniLayer/omnicore,HashUnlimited/Einsteinium-Unlimited,itmanagerro/tresting,oklink-dev/bitcoin,litecoin-project/litecore-litecoin,Electronic-Gulden-Foundation/egulden,bdelzell/creditcoin-org-creditcoin,magacoin/magacoin,jl2012/litecoin,okinc/bitcoin,zetacoin/zetacoin,magacoin/magacoin,okinc/bitcoin,EntropyFactory/creativechain-core,oklink-dev/bitcoin,ShadowMyst/creativechain-core,EntropyFactory/creativechain-core,zcoinofficial/zcoin,jl2012/litecoin,jl2012/litecoin,lbrtcoin/albertcoin,gravio-net/graviocoin,lbrtcoin/albertcoin,shaolinfry/litecoin,lbrtcoin/albertcoin,shaolinfry/litecoin,lbrtcoin/albertcoin,gravio-net/graviocoin,cannabiscoindev/cannabiscoin420,lbrtcoin/albertcoin,litecoin-project/litecore-litecoin,itmanagerro/tresting,ShadowMyst/creativechain-core,zetacoin/zetacoin,oklink-dev/bitcoin,EntropyFactory/creativechain-core,emc2foundation/einsteinium,bitcoinplusorg/xbcwalletsource,bdelzell/creditcoin-org-creditcoin,zetacoin/zetacoin,bdelzell/creditcoin-org-creditcoin,Electronic-Gulden-Foundation/egulden,cannabiscoindev/cannabiscoin420,bitcoinplusorg/xbcwalletsource,zetacoin/zetacoin,OmniLayer/omnicore,zcoinofficial/zcoin,Electronic-Gulden-Foundation/egulden,HashUnlimited/Einsteinium-Unlimited,jl2012/litecoin,bdelzell/creditcoin-org-creditcoin,lbrtcoin/albertcoin,itmanagerro/tresting,emc2foundation/einsteinium,cannabiscoindev/cannabiscoin420,metacoin/florincoin,lbrtcoin/albertcoin,metacoin/florincoin,ShadowMyst/creativechain-core,okinc/bitcoin,funkshelper/woodcore,Electronic-Gulden-Foundation/egulden,zcoinofficial/zcoin,bitcoinplusorg/xbcwalletsource,magacoin/magacoin,itmanagerro/tresting,oklink-dev/bitcoin,lbrtcoin/albertcoin,magacoin/magacoin,ShadowMyst/creativechain-core,cannabiscoindev/cannabiscoin420,okinc/bitcoin,funkshelper/woodcore,magacoin/magacoin,emc2foundation/einsteinium,metacoin/florincoin,zcoinofficial/zcoin,zcoinofficial/zcoin,metacoin/florincoin,ShadowMyst/creativechain-core,HashUnlimited/Einsteinium-Unlimited,emc2foundation/einsteinium,Electronic-Gulden-Foundation/egulden,zetacoin/zetacoin,lbrtcoin/albertcoin,itmanagerro/tresting,EntropyFactory/creativechain-core,shaolinfry/litecoin,lbrtcoin/albertcoin,shaolinfry/litecoin,OmniLayer/omnicore,gravio-net/graviocoin,zcoinofficial/zcoin,litecoin-project/litecore-litecoin,metacoin/florincoin,zcoinofficial/zcoin,jl2012/litecoin,gravio-net/graviocoin,oklink-dev/bitcoin,shaolinfry/litecoin,zcoinofficial/zcoin,emc2foundation/einsteinium,OmniLayer/omnicore,bdelzell/creditcoin-org-creditcoin,emc2foundation/einsteinium,magacoin/magacoin,shaolinfry/litecoin,EntropyFactory/creativechain-core,bitcoinplusorg/xbcwalletsource,OmniLayer/omnicore,litecoin-project/litecore-litecoin,metacoin/florincoin,cannabiscoindev/cannabiscoin420,litecoin-project/litecore-litecoin,ShadowMyst/creativechain-core,HashUnlimited/Einsteinium-Unlimited,zcoinofficial/zcoin,okinc/bitcoin,bdelzell/creditcoin-org-creditcoin,itmanagerro/tresting,lbrtcoin/albertcoin,gravio-net/graviocoin,OmniLayer/omnicore,funkshelper/woodcore,funkshelper/woodcore