refactor(metadata): move metadata attributes to static metadata [part 2/12]

[glevco]

Motivation

This PR continues and completes the implementation for a working version of the static metadata refactor started in the previous PR, #1013. Read its description for more detailed information.

It moves the height, min_height, and feature_activation_bit_counts metadata attributes to the new static structure. The feature_states attribute will be migrated in the next PR.

As a consequence, it introduces several benefits for metadata handling, including:

• Blocks and Transactions now have separate types for their static metadata attributes, which are different. No more handling of non-existent attributes for different types, like setting height=0 for transactions.
• All vertices are required to have static metadata set before they're saved to the storage, meaning when a vertex is retrieved from the storage, it's guaranteed to have static metadata. No need to perform updates and such.
• Static metadata can be interpreted more as attributes that are as constant and present as intrinsic vertex attributes, and less like dynamic metadata attributes (like voided_by and validation).

Acceptance Criteria

• Remove height, min_height, and feature_activation_bit_counts attributes from metadata, moving them to static metadata.
  • Provide new equivalent metadata properties that are a forward from static metadata, for backwards compatibility.
  • Keep those properties in the to_json() method, for backwards compatibility with APIs and etc.
• Move some metadata-related methods from BaseTransaction and its subclasses to the static metadata dataclasses, and remove some that are not necessary anymore.
  • Changes were made so they do not depend on a storage anymore.
• Implement create() and create_from_storage() methods for static metadata dataclasses.
• Implement migrate_static_metadata Migration to move existing metadata attributes to the new static metadata structure.
• Changes in TransactionStorage and its subclasses:
  • Save static metadata in save_transaction() and retrieve/set it in get_transaction() and get_all_transactions().
  • Remove _validate_block_height_metadata().
  • Implement iter_all_raw_metadata() method used in the migration.
• Fix and update code and tests accordingly.

Breaking Changes

• Before, all API calls that returned metadata included both a height and a feature_activation_bit_counts field for all vertices. For transactions, they were always falsy values (0, None, or []). Now, they were removed from transactions and are only present for blocks.

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

Attention: Patch coverage is 83.20312% with 43 lines in your changes missing coverage. Please review.

Project coverage is 84.54%. Comparing base (9bce2fa) to head (701b787).
Report is 2 commits behind head on master.

Files	Patch %	Lines
hathor/transaction/storage/rocksdb_storage.py	48.57%	18 Missing ⚠️
...tion/storage/migrations/migrate_static_metadata.py	53.84%	12 Missing ⚠️
hathor/manager.py	50.00%	1 Missing and 4 partials ⚠️
hathor/transaction/transaction_metadata.py	86.95%	0 Missing and 3 partials ⚠️
...on/storage/migrations/remove_first_nop_features.py	33.33%	2 Missing ⚠️
hathor/mining/block_template.py	0.00%	1 Missing ⚠️
hathor/transaction/storage/cache_storage.py	75.00%	1 Missing ⚠️
hathor/verification/transaction_verifier.py	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1014      +/-   ##
==========================================
- Coverage   84.90%   84.54%   -0.37%     
==========================================
  Files         316      317       +1     
  Lines       24079    24149      +70     
  Branches     3645     3665      +20     
==========================================
- Hits        20445    20417      -28     
- Misses       2918     3018     +100     
+ Partials      716      714       -2     

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