refactor: Prepare for sync-v2

[msbrogli]

Motivation

This PR contains refactors needed by sync v2. These changes DO NOT change any external behavior. They are mostly adjustments and fixes so tests can be easily adapted to run with sync v2.

Acceptance Criteria

1. Add asserts on FeatureService to gracefully fail and prevent infinite loop.
2. Fix scope verification on TransactionStorage.get_all_transactions().
3. Assert that a transaction is fully validated on ConsensusAlgorithm.update().
4. Fix RocksDBHeightIndex._add() method. It was wrongfully identifying a reorg when a reorg wasn't happening.
5. Prepare HathorManager to initialize with partial and invalid transactions stored in the database.
6. Add missing @abstractmethod decorators on SyncManager.
7. Improve simulator FakeConnection with an auto-reconnect feature.
8. Add FakeConnection.reconnect() and FakeConnection.is_both_synced() methods.
9. Add simulator triggers (StopWhenTrue, StopWhenSynced, and All).
10. Add private attribute TransactionRocksDBStorage. _rocksdb_storage: RocksDBStorage.
11. Change tests/p2p/test_sync_rate_limiter.py to run for sync v1 only since it tests a rate limiter that exists only in sync v1.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

Merging #697 (3695ad2) into master (67e0848) will decrease coverage by 0.12%.
The diff coverage is 66.66%.

❗ Current head 3695ad2 differs from pull request most recent head 78123f0. Consider uploading reports for the commit 78123f0 to get more accurate results

@@            Coverage Diff             @@
##           master     #697      +/-   ##
==========================================
- Coverage   84.13%   84.01%   -0.12%     
==========================================
  Files         246      246              
  Lines       20450    20519      +69     
  Branches     2760     2769       +9     
==========================================
+ Hits        17206    17240      +34     
- Misses       2672     2706      +34     
- Partials      572      573       +1     

Impacted Files	Coverage Δ
hathor/transaction/base_transaction.py	91.60% <ø> (+0.97%)	⬆️
hathor/transaction/block.py	91.45% <0.00%> (-0.79%)	⬇️
hathor/util.py	81.30% <ø> (ø)
hathor/manager.py	77.46% <38.70%> (+0.21%)	⬆️
hathor/simulator/fake_connection.py	71.18% <73.91%> (-11.55%)	⬇️
hathor/simulator/trigger.py	95.83% <87.50%> (-4.17%)	⬇️
hathor/consensus/consensus.py	97.87% <100.00%> (+0.02%)	⬆️
hathor/feature_activation/feature_service.py	97.53% <100.00%> (+0.06%)	⬆️
hathor/indexes/rocksdb_height_index.py	95.55% <100.00%> (ø)
hathor/p2p/sync_manager.py	100.00% <100.00%> (ø)
... and 2 more

... and 3 files with indirect coverage changes