objstore: fix read position on retry when reading a file range using s3 (#59694)

[ti-chi-bot]

This is an automated cherry-pick of #59694

What problem does this PR solve?

Issue Number: close #50451

Problem Summary:

What changed and how does it work?

when reading a file range using s3, the pos must be set, as we will use it as the start position when retry

Check List

Tests

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

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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[Benjamin2037]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-03-13 07:58:08.128993909 +0000 UTC m=+429043.734522828: ☑️ agreed by Benjamin2037.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release-8.1@7b51a54). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #60055   +/-   ##
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  Coverage               ?   71.2115%           
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  Files                  ?       1468           
  Lines                  ?     424045           
  Branches               ?          0           
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  Hits                   ?     301969           
  Misses                 ?     101533           
  Partials               ?      20543           

Flag	Coverage Δ
unit	71.2115% <50.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9656% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	41.4279% <0.0000%> (?)

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