feat(nano): generalize faux-immutability

[glevco]

Motivation

Generalize the immutability structures created for NanoRNG so it can be reused on other classes.

Acceptance Criteria

• Implement FauxImmutable class, with a metaclass, that defines faux-immutability behavior for its subclasses.
• Update NanoRNG to use FauxImmutable instead of its own ad-hoc solution. No behavior should change, except for:
  • Some error messages are changed.
  • You don't need NanoRNG.create_with_shell(), simply doing NanoRNG() will always provide a shell.

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

❌ Patch coverage is 98.03922% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.71%. Comparing base (4b8dbc6) to head (339db24).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
hathor/nanocontracts/faux_immutable.py	97.61%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1349      +/-   ##
==========================================
+ Coverage   85.66%   85.71%   +0.04%     
==========================================
  Files         426      427       +1     
  Lines       32270    32304      +34     
  Branches     5025     5032       +7     
==========================================
+ Hits        27645    27690      +45     
+ Misses       3613     3602      -11     
  Partials     1012     1012              

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The base branch was changed.

[github-actions]

Bencher Report

Branch	feat/nano/faux-immutability
Testbed	ubuntu-22.04

Click to view all benchmark results

Benchmark	Latency	Benchmark Result minutes (m) (Result Δ%)	Lower Boundary minutes (m) (Limit %)	Upper Boundary minutes (m) (Limit %)
sync-v2 (up to 20000 blocks)	📈 view plot 🚷 view threshold	1.70 m (+3.68%) Baseline: 1.64 m	1.48 m (86.80%)	1.81 m (94.26%)

🐰 View full continuous benchmarking report in Bencher