refactor file writing and optimize hard link logic

[jinronga]

• Replace local file writing operations with helper functions to improve code reuse
• Extract hard link logic into a separate file to enhance maintainability
• Add hard link implementation for Windows systems
• Remove unnecessary code to simplify the file writing process

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

❌ Patch coverage is 15.62500% with 81 lines in your changes missing coverage. Please review.
✅ Project coverage is 32.62%. Comparing base (791093d) to head (c1f0c3b).
⚠️ Report is 40 commits behind head on main.

Files with missing lines	Patch %	Lines
client/daemon/test/mock_helper.go	0.00%	36 Missing ⚠️
client/daemon/storage/hardlink_unix.go	19.44%	28 Missing and 1 partial ⚠️
client/daemon/storage/piece_io.go	20.00%	14 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4200      +/-   ##
==========================================
- Coverage   32.66%   32.62%   -0.05%     
==========================================
  Files         350      353       +3     
  Lines       41188    41223      +35     
==========================================
- Hits        13456    13449       -7     
- Misses      26842    26888      +46     
+ Partials      890      886       -4     

Flag	Coverage Δ
unittests	32.62% <15.62%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
client/daemon/storage/local_storage.go	32.63% <100.00%> (+1.23%)	⬆️
client/daemon/storage/local_storage_subtask.go	27.15% <100.00%> (+0.30%)	⬆️
client/daemon/storage/piece_io.go	20.00% <20.00%> (ø)
client/daemon/storage/hardlink_unix.go	19.44% <19.44%> (ø)
client/daemon/test/mock_helper.go	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

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[gaius-qi]

@jinronga Golang client may not be maintained in the future, so you can take a look at the rust client, refer to https://github.com/dragonflyoss/client.