Merge bitcoin/bitcoin#24543: net processing: Move remaining globals into PeerManagerImpl

778343a scripted-diff: Rename PeerManagerImpl members (dergoegge)
91c3392 [net processing] Move nHighestFastAnnounce into PeerManagerImpl (dergoegge)
10b83e2 [net processing] Move block cache state into PeerManagerImpl (dergoegge)
a4c55a9 [net processing] Inline and simplify UpdatePreferredDownload (dergoegge)
490c08f [net processing] Move nPreferredDownload into PeerManagerImpl (dergoegge)
a292df2 [net processing] Move mapNodeState into PeerManagerImpl (dergoegge)
37ecaf3 [net processing] Move CNodeState declaration above PeerManagerImpl (dergoegge)

Pull request description:

  This PR moves the remaining net processing globals into `PeerManagerImpl`. This will make testing the peer manager in isolation easier and also acts as a code clean up.

ACKs for top commit:
  jnewbery:
    Code review ACK 778343a
  MarcoFalke:
    ACK 778343a 🗒

Tree-SHA512: 4f22105d1de37b94c3ef349f38784a30cf8d450d394a6a7849e5bd78940a71e3edbffa3d25e8efb35d7f698fd255f199de7bd4c33e23af5621a6e4e67ed43cb5

Author: MacroFake