fix(core): rework stored cell hashes

[Rexagon]

There is a couple of improvements which we could make for stored cells:

• Don't store repr hash since it is already a cell hash;
• Properly route cell hashes for lower levels of pruned cells.

For now this is a breaking change, but the migration is possible.

• Compare disk usage (done: 23 GiB old vs 16 GiB new on testnet after the cold boot only);
• Add migration (done: reassembles cell values while also removing items with zero rc; runs for ~1 minute).

[github-actions]

🧪 Network Tests

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• Run specific test: gh workflow run network-tests.yml -f pr_number=994 -f test_selection=ping-pong

Test types: destroyable, ping-pong, one-to-many-internal-messages, fq-deploy, nft-index, persistent-sync

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[codecov]

Codecov Report

❌ Patch coverage is 51.94175% with 99 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.60%. Comparing base (7d0cd44) to head (ef22e4c).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
core/src/storage/db/migrations.rs	0.00%	80 Missing ⚠️
core/src/storage/shard_state/cell_storage.rs	88.59%	1 Missing and 12 partials ⚠️
core/src/storage/db/mod.rs	40.00%	2 Missing and 1 partial ⚠️
core/src/block_strider/starter/cold_boot.rs	0.00%	1 Missing ⚠️
...src/storage/persistent_state/shard_state/writer.rs	66.66%	0 Missing and 1 partial ⚠️
core/src/storage/shard_state/store_state_raw.rs	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #994      +/-   ##
==========================================
- Coverage   54.76%   54.60%   -0.17%     
==========================================
  Files         362      364       +2     
  Lines       63573    63837     +264     
  Branches    63573    63837     +264     
==========================================
+ Hits        34814    34856      +42     
- Misses      26833    27030     +197     
- Partials     1926     1951      +25     

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