feat: remove peers that were disconnected and cant be reconnected anymore

[pedroferreira1]

Motivation

https://github.com/HathorNetwork/internal-issues/issues/73

Acceptance criteria

Peers that have no entrypoints and have disconnected must be removed from the known peers list because there is no more use for them.

[codecov]

Codecov Report

Merging #365 (b675333) into dev (79e47aa) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              dev     #365   +/-   ##
=======================================
  Coverage   82.76%   82.77%           
=======================================
  Files         166      166           
  Lines       15175    15181    +6     
  Branches     2144     2146    +2     
=======================================
+ Hits        12560    12566    +6     
  Misses       2182     2182           
  Partials      433      433           

Impacted Files	Coverage Δ
hathor/p2p/manager.py	70.00% <100.00%> (+0.22%)	⬆️
hathor/p2p/peer_storage.py	100.00% <100.00%> (ø)

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