refactor: refactor the e2e file server

[chlins]

Description

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.12%. Comparing base (25a4b53) to head (731cd31).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3741      +/-   ##
==========================================
- Coverage   35.14%   35.12%   -0.03%     
==========================================
  Files         336      336              
  Lines       37852    37852              
==========================================
- Hits        13303    13295       -8     
- Misses      23720    23725       +5     
- Partials      829      832       +3     

Flag	Coverage Δ
unittests	35.12% <ø> (-0.03%)	⬇️

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see 3 files with indirect coverage changes

[gaius-qi]

LGTM

[gaius-qi]

LGTM