feat(network): rewire PMA consumers to use transport and connected_peers (8/n)

[shreyan-gupta]

• Block/headers/epoch-sync broadcast → transport.broadcast_message(T2, ...)
• Per-peer sends (BlockRequest, etc.) → transport.send_message(T2, ...)
• SyncSnapshotHosts broadcast → transport.broadcast_message(T2, ...)
• Highest-height peer queries → state.peers.tier2() + to_highest_height_peer_info helper
• Peer matching/filtering → state.peers.tier2() instead of state.tier2.load().ready

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.47%. Comparing base (6ff3b8b) to head (62b76bf).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...ain/network/src/peer_manager/peer_manager_actor.rs	87.50%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #15576   +/-   ##
=======================================
  Coverage   69.46%   69.47%           
=======================================
  Files         942      942           
  Lines      214969   214991   +22     
  Branches   214969   214991   +22     
=======================================
+ Hits       149334   149357   +23     
- Misses      59716    59720    +4     
+ Partials     5919     5914    -5     

Flag	Coverage Δ
pytests-nightly	1.14% <0.00%> (-0.01%)	⬇️
unittests	68.91% <87.50%> (+<0.01%)	⬆️
unittests-nightly	69.01% <87.50%> (+<0.01%)	⬆️

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