Revert "refactor of MConnection internals"

[pompon0]

Reverts #322

I've implemented some additional tests which indicate regression caused by this PR.
I don't know what is the issue exactly yet, but let's revert this PR for now.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 26, 2025, 1:52 PM

[codecov]

Codecov Report

❌ Patch coverage is 80.30769% with 64 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.02%. Comparing base (a32efe0) to head (58490de).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/p2p/conn/connection.go	82.84%	41 Missing and 12 partials ⚠️
libs/utils/scope/global.go	0.00%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #324      +/-   ##
==========================================
+ Coverage   56.97%   57.02%   +0.05%     
==========================================
  Files         259      258       -1     
  Lines       34483    34471      -12     
==========================================
+ Hits        19647    19658      +11     
+ Misses      13255    13227      -28     
- Partials     1581     1586       +5     

Files with missing lines	Coverage Δ
internal/p2p/router.go	78.13% <100.00%> (+3.03%)	⬆️
internal/p2p/transport_memory.go	86.25% <100.00%> (+0.89%)	⬆️
libs/utils/proto.go	1.81% <ø> (+0.20%)	⬆️
libs/utils/wait.go	9.23% <ø> (+1.01%)	⬆️
libs/utils/scope/global.go	0.00% <0.00%> (ø)
internal/p2p/conn/connection.go	80.05% <82.84%> (-4.98%)	⬇️

... and 10 files with indirect coverage changes

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