Antalya 25.8 Backport of #103542 - Fix S3/GCS "Response checksums mismatch" with aws-sdk-cpp 1.11.771

[CarlosFelipeOR]

(cherry picked from commit 659369e)
Fix #1708

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

...

Documentation entry for user-facing changes

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CI/CD Options

Exclude tests:

• Fast test
• Integration Tests
• Stateless tests
• Stateful tests
• Performance tests
• All with ASAN
• All with TSAN
• All with MSAN
• All with UBSAN
• All with Coverage
• All with Aarch64
• All Regression
• Disable CI Cache

Regression jobs to run:

• Fast suites (mostly <1h)
• Aggregate Functions (2h)
• Alter (1.5h)
• Benchmark (30m)
• ClickHouse Keeper (1h)
• Iceberg (2h)
• LDAP (1h)
• Parquet (1.5h)
• RBAC (1.5h)
• SSL Server (1h)
• S3 (2h)
• S3 Export (2h)
• Swarms (30m)
• Tiered Storage (2h)

[github-actions]

Workflow [PR], commit [70520c2]

[DimensionWieldr]

This PR is an S3 client checksum-mode fix for the specific Response checksums mismatch regression in #1708. Current fails are not blocking:

• Regression failures: settings (known outdated suite) and swarms (known unstable/network-heavy scenarios), not the AWS/GCS checksum regression path this PR targets.
• Integration failures: unrelated flaky/broken tests and timeout-prone tests, not related to deterministic checksum-mismatch startup failure from #1708.
• Stateless failures: mostly runner/environment instability (startup/port collisions, infra script issues, intermittent external S3 reachability), not a deterministic regression caused by this PR.

@CarlosFelipeOR Can you sign-off your commit so DCO check passes?

Otherwise LGTM

[CarlosFelipeOR]

This change was also cherry-picked by Andrey in PR #1679 (794a72f), and it has already been merged. So this PR is no longer needed.