Split storage sync P2P protocol (manual fallback)

[martintomazic]

As discussed in #6262 it might be simpler to manually handle fallback to the legacy protocol.

Closes #5751.

Regarding the style, I would prefer to keep it consistent with other p2p packages even if not optimal: #6262 (comment)

[netlify]

✅ Deploy Preview for oasisprotocol-oasis-core canceled.

Name	Link
🔨 Latest commit	c02ca0c
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[codecov]

Codecov Report

❌ Patch coverage is 82.47012% with 44 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.70%. Comparing base (a81a9dd) to head (c02ca0c).
⚠️ Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
go/worker/storage/committee/checkpoint_sync.go	72.88%	16 Missing ⚠️
go/worker/storage/p2p/checkpointsync/server.go	73.68%	6 Missing and 4 partials ⚠️
go/worker/storage/p2p/diffsync/server.go	73.33%	5 Missing and 3 partials ⚠️
go/worker/storage/committee/node.go	80.64%	5 Missing and 1 partial ⚠️
go/worker/storage/p2p/checkpointsync/client.go	95.45%	1 Missing and 1 partial ⚠️
go/worker/storage/p2p/diffsync/client.go	88.23%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6277      +/-   ##
==========================================
+ Coverage   64.62%   64.70%   +0.08%     
==========================================
  Files         690      696       +6     
  Lines       67593    67803     +210     
==========================================
+ Hits        43680    43870     +190     
- Misses      18855    18880      +25     
+ Partials     5058     5053       -5     

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[peternose]

Looks good to me 👍