test: deflake stream compat coverage

[mcollina]

This relates to...

Fixes: #5207

Rationale

test/stream-compat.js could finish with servers and clients still mid-lifecycle, which makes the unexpected disconnect guards race with teardown on CI.

Changes

• switch the tests to await server startup explicitly with once(..., 'listening')
• use per-test teardown via the original test context instead of file-level after() hooks
• close active server connections before shutting test servers down
• fully drain the response body in IncomingMessage before completing the test

Features

N/A

Bug Fixes

• deflake test/stream-compat.js

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.28%. Comparing base (20711c6) to head (33762c7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5209      +/-   ##
==========================================
+ Coverage   93.27%   93.28%   +0.01%     
==========================================
  Files         110      110              
  Lines       36349    36349              
==========================================
+ Hits        33904    33908       +4     
+ Misses       2445     2441       -4     

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