refactor(scripts): modularize script files

[glevco]

Motivation

Refactor code so the single scripts.py file is broken into multiple modules, improving organization and maintainability. No behavior is changed by this PR, code is only moved between files. The only active changes are in imports to fix circular dependencies after the refactor.

Acceptance Criteria

1. Move HathorScript to its own file
2. Move BaseScript to its own file
3. Move P2PKH to its own file
4. Move MultiSig to its own file
5. Move NanoContractMatchValues to its own file
6. Move Opcode and functions to their own file
7. Remaining functions from the scripts file moved to either construct or execute modules
8. Fix imports and linter issues

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

Comparison is base (3c8698e) 85.08% compared to head (7c774b1) 85.07%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #811      +/-   ##
==========================================
- Coverage   85.08%   85.07%   -0.02%     
==========================================
  Files         276      284       +8     
  Lines       22514    22576      +62     
  Branches     3430     3430              
==========================================
+ Hits        19157    19207      +50     
- Misses       2674     2683       +9     
- Partials      683      686       +3     

Files	Coverage Δ
hathor/transaction/scripts/__init__.py	100.00% <100.00%> (ø)
hathor/transaction/scripts/base_script.py	100.00% <100.00%> (ø)
hathor/transaction/scripts/hathor_script.py	100.00% <100.00%> (ø)
hathor/transaction/scripts/multi_sig.py	97.67% <97.67%> (ø)
hathor/transaction/scripts/p2pkh.py	96.72% <96.72%> (ø)
hathor/transaction/scripts/execute.py	96.74% <96.74%> (ø)
hathor/transaction/scripts/opcode.py	97.02% <97.02%> (ø)
.../transaction/scripts/nano_contract_match_values.py	87.87% <87.87%> (ø)
hathor/transaction/scripts/construct.py	81.98% <81.98%> (ø)

... and 5 files with indirect coverage changes

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