[net] Consolidate logic around calling CAddrMan::Connected()
[net] Consolidate logic around calling CAddrMan::Connected()

Summary:
Currently, the logic around whether we called `CAddrMan::Connected()` for
a peer is spread between verack processing (where we discard inbound
peers) and `FinalizeNode` (where we discard misbehaving and
block-relay-only peers). Consolidate that logic to a single place.

Also remove the `CNode.fCurrentlyConnected` bool, which is now
redundant. We can rely on `CNode.fSuccessfullyConnected`, since the two
bools were only ever flipped to true in the same place.

This is a backport of [[https://github.com/bitcoin/bitcoin/pull/20291 | core#20291]] [1/2]
https://github.com/bitcoin/bitcoin/pull/20291/commits/eefe19471868ef0cdc9d32473d0b57015e7647ee

Depends on D10697

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10698

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