refactor(fees): simplify fee abstractions

[glevco]

Motivation

Simplify the fee-related logic by removing intermediary models and abstractions. This is only a code cleanup and no behavior should change.

Acceptance Criteria

• Remove syscall balance rules abstractions, changing the unnecessary class polymorphism to simple functions with match statements.
• No changes in behavior.

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 96.96970% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.10%. Comparing base (aea71a3) to head (23df2df).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
hathor/nanocontracts/runner/index_records.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1469      +/-   ##
==========================================
- Coverage   86.13%   86.10%   -0.04%     
==========================================
  Files         437      437              
  Lines       34081    33987      -94     
  Branches     5329     5316      -13     
==========================================
- Hits        29357    29264      -93     
+ Misses       3680     3678       -2     
- Partials     1044     1045       +1     

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[github-actions]

Bencher Report

Branch	refactor/fees/remove-abstractions
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	1.73 m (-0.15%) Baseline: 1.73 m	1.56 m (90.13%)	2.08 m (83.21%)

🐰 View full continuous benchmarking report in Bencher