release-8.5: Fix prefetch buffer and GCS EOF retry (#59496, #59851)

[GMHDBJD]

This PR manually cherry-picks two PRs to release-8.5 to resolve a dependency.

---

cherry-pick #59496
cherry-pick #59851

What problem does this PR solve?

Issue Number: close #59495, close #59754

Problem Summary:
This PR addresses two separate but related issues:

1. The prefetch buffer was not always being fully filled, potentially leading to inefficient reads.
2. A bug in Go's net/http library can cause io.EOF errors when using GCS, which were not being retried, causing operations to fail.

What changed and how does it work?

1. Prefetch Buffer Fix: Switched to using io.ReadFull to ensure the prefetch buffer is always filled completely.
2. GCS EOF Retry: Added a workaround in the GCS storage layer to specifically retry on io.EOF errors, making the connection more resilient to the underlying library bug.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

Release note

None

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.5@310cdcc). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #62061   +/-   ##
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  Coverage               ?   57.8742%           
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  Lines                  ?     633399           
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  Hits                   ?     366575           
  Misses                 ?     242298           
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Flag	Coverage Δ
integration	38.7399% <63.6363%> (?)
unit	72.7735% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	63.2388% <0.0000%> (?)

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[Benjamin2037]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, D3Hunter

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-07-01 01:12:06.803028728 +0000 UTC m=+1357379.526207709: ☑️ agreed by Benjamin2037.
• 2025-07-01 02:15:58.67718294 +0000 UTC m=+1361211.400361917: ☑️ agreed by D3Hunter.

[hawkingrei]

/retest

[GMHDBJD]

/retest

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[D3Hunter]

/retest

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[D3Hunter]

/retest

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