Introduce mixins for the fn-tests and use in the existing tests.

[evgenyzdanovich]

Description

Introduce mixins for the fn-tests and use in the existing tests.
Also, minor refactoring and cleanup.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature/Enhancement (non-breaking change which adds functionality or enhances an existing one)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor
• New or updated tests
• Dependency Update

Notes to Reviewers

Checklist

• I have performed a self-review of my code.
• I have commented my code where necessary.
• I have updated the documentation if needed.
• My changes do not introduce new warnings.
• I have added tests that prove my changes are effective or that my feature works.
• New and existing tests pass with my changes.

Related Issues

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.95%. Comparing base (0db65b9) to head (d79dab4).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #634      +/-   ##
==========================================
- Coverage   55.97%   55.95%   -0.03%     
==========================================
  Files         315      315              
  Lines       33428    33428              
==========================================
- Hits        18712    18704       -8     
- Misses      14716    14724       +8     

see 5 files with indirect coverage changes

[github-actions]

Commit: 71fbe49

SP1 Performance Test Results

program	cycles	success
BTC_BLOCKSPACE	30,357,421	✅
EL_BLOCK	98,534	✅
CL_BLOCK	57,370	✅
L1_BATCH	30,387,324	✅
L2_BATCH	5,473	✅
CHECKPOINT	15,895	✅