refactor(settings): refactor genesis module

[glevco]

Depends on #787

Motivation

This PR not only removes any usage of global settings from the genesis module, but it also substitutes all global variables defined in this module by functions. It also includes some simplifications in code using that module.

Acceptance Criteria

• Remove BLOCK_GENESIS, TX_GENESIS1, TX_GENESIS2, GENESIS, GENESIS_HASHES, GENESIS_HASH global variables and implement, respectively, get_genesis_block(), get_genesis_tx1(), get_genesis_tx2(), get_all_genesis(), get_all_genesis_hashes(), get_genesis_hash(). As these are not shared instances anymore, it's safe to manipulate the returned instance in tests, for example.
• Simplify get_genesis_hash() and is_genesis() implementations.
• Remove _get_genesis_transactions_unsafe() function as after all refactors it was only used in one place.
• Change CliBuilder to use the existing get_genesis_short_hash() function.
• Removed height_index.BLOCK_GENESIS_ENTRY global variable and refactored it into HeightIndex.get_genesis_block_entry().
• Update all code using removed global variables.

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: 11 lines in your changes are missing coverage. Please review.

Comparison is base (c700dc5) 84.65% compared to head (96b93db) 84.69%.
Report is 1 commits behind head on master.

❗ Current head 96b93db differs from pull request most recent head 88ef27f. Consider uploading reports for the commit 88ef27f to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #794      +/-   ##
==========================================
+ Coverage   84.65%   84.69%   +0.04%     
==========================================
  Files         264      264              
  Lines       22034    22019      -15     
  Branches     3369     3364       -5     
==========================================
- Hits        18652    18649       -3     
+ Misses       2726     2717       -9     
+ Partials      656      653       -3     

Files	Coverage Δ
hathor/builder/builder.py	91.02% <ø> (ø)
hathor/builder/cli_builder.py	74.35% <100.00%> (-0.14%)	⬇️
hathor/indexes/base_index.py	100.00% <100.00%> (ø)
hathor/indexes/height_index.py	96.61% <100.00%> (ø)
hathor/indexes/memory_height_index.py	83.33% <100.00%> (ø)
hathor/indexes/memory_info_index.py	91.83% <100.00%> (+0.17%)	⬆️
hathor/indexes/rocksdb_height_index.py	94.17% <100.00%> (+0.05%)	⬆️
hathor/p2p/utils.py	74.10% <100.00%> (+0.23%)	⬆️
hathor/simulator/simulator.py	94.61% <100.00%> (-0.04%)	⬇️
hathor/transaction/base_transaction.py	94.16% <100.00%> (ø)
... and 4 more

... and 6 files with indirect coverage changes

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The base branch was changed.

[glevco]

@msbrogli @jansegre as we discussed, in a86c175 I made the following changes:

• In HathorSettings:
  • Rename GENESIS_TIMESTAMP to GENESIS_BLOCK_TIMESTAMP.
  • Add GENESIS_TX1_TIMESTAMP and GENESIS_TX2_TIMESTAMP calculated properties. This simplifies some use cases of the removed genesis module functions.
• In genesis module:
  • Rename get_genesis_hash() to get_representation_for_all_genesis().
  • Remove get_genesis_block(), get_genesis_tx1(), get_genesis_tx2(), and get_all_genesis().
• In TransactionStorage:
  • Remove _get_genesis_from_settings().
  • Add _construct_genesis_block(), _construct_genesis_tx1(), and _construct_genesis_tx2().
• In test_tx_storage I had to remove part of a test, since it doesn't make sense anymore.
• In tests/utils remove get_min_timestamp().