```
Onion peers are disadvantaged under our eviction criteria, so prevent
eventual eviction of them in the presence of contention for inbound
slots by reserving some slots for localhost peers (sorted by longest
uptime).
Block-relay-only connections exist as a protection against eclipse
attacks, by creating a path for block propagation that may be unknown to
adversaries. Protect against inbound peer connection slot attacks from
disconnecting such peers by attempting to protect up to 8 peers that are
not relaying transactions but appear to be full-nodes, sorted by recency
of last delivered block.
```
Backport of core#19670.
Note that tests will be added when porting this PR:
https://github.com/bitcoin/bitcoin/pull/20477
Ref T1611.