De-duplicate peer connections during replication session updates

[sandreae]

Because peers listen on multiple local network addresses and often on discovery dial each other concurrently, it's very hard to set a "one connection per-peer" limit on established connections (we have managed to limit it to max two connections now, one as listener, one as dialer). We can however filter out any duplicate connections when choosing peers to initiate replication sessions with.

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• Add tests that cover your changes
• Add this PR to the Unreleased section in CHANGELOG.md
• Link this PR to any issues it closes
• New files contain a SPDX license header

[codecov]

Codecov Report

Patch coverage: 90.90% and no project coverage change.

Comparison is base (51d37b6) 92.30% compared to head (1c92dc3) 92.31%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #525   +/-   ##
=======================================
  Coverage   92.30%   92.31%           
=======================================
  Files         102      102           
  Lines       16070    16073    +3     
=======================================
+ Hits        14834    14837    +3     
  Misses       1236     1236           

Files Changed	Coverage Δ
aquadoggo/src/replication/service.rs	75.64% <90.90%> (+0.19%)	⬆️

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