Add polkadot_parachain_peer_connectivity metric#8973

AndreiEres merged 3 commits intomasterparitytech/polkadot-sdk:masterfrom

AndreiEres/issue8911-Add-histogram-alternative-to-polkadot_parachain_peer_countparitytech/polkadot-sdk:AndreiEres/issue8911-Add-histogram-alternative-to-polkadot_parachain_peer_countCopy head branch name to clipboard