fix(fs/unstable): fix node.js test runner, fix readTextFile and copyFile in Node.js

[0f-0b]

This PR changes the Node.js test runner to import the correct modules and fixes the new test failures.

[codecov]

Codecov Report

Attention: Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.

Project coverage is 95.98%. Comparing base (71c828a) to head (99967fb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
fs/unstable_read_text_file.ts	14.28%	6 Missing ⚠️
fs/unstable_copy_file.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6441      +/-   ##
==========================================
- Coverage   95.98%   95.98%   -0.01%     
==========================================
  Files         564      564              
  Lines       42482    42481       -1     
  Branches     6394     6394              
==========================================
- Hits        40775    40774       -1     
  Misses       1668     1668              
  Partials       39       39              

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[kt3k]

Thank you! @0f-0b

LGTM