[net] Fix bug where AddrFetch connections would be counted as outbound full relay
[net] Fix bug where AddrFetch connections would be counted as outbound full relay

Summary:
```
The desired logic is for us to only open feeler connections after we
have hit the max count for outbound full relay connections.  A short
lived AddrFetch connection (previously called oneshot) could cause
ThreadOpenConnections to miscount and mistakenly open a feeler instead
of full relay.
```

Partial backport (15/19) of core [[https://github.com/bitcoin/bitcoin/pull/19316 | PR19316]]:
https://github.com/bitcoin/bitcoin/pull/19316/commits/35839e963bf61d2da0d12f5b8cea74ac0e0fbd7b

Depends on D8724.

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8725

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