Purpose

Linked issue: #357, follow-up to #433

Address the remaining correctness, robustness, diagnostics, and build issues in the
lightweight S3 filesystem implementation:

• keep the asynchronous executor alive independently from individual S3 clients
• preserve virtual-hosted addressing for compatible HTTPS endpoints and correctly handle IPv6
  endpoint authorities
• parse ListObjectsV2 ISO 8601 modification times
• add configurable request and low-speed timeouts
• retain bounded S3 error responses and bucket-region headers for actionable diagnostics
• cover not-found responses, asynchronous client release, endpoint addressing, timestamps,
  retries, and timeouts
• declare the required CURL, OpenSSL, and Arrow link dependencies for supported static and
  shared builds

Tests

• pre-commit run --files CMakeLists.txt cmake_modules/ThirdpartyToolchain.cmake src/paimon/CMakeLists.txt src/paimon/common/fs/http_client.cpp src/paimon/common/fs/http_client.h src/paimon/common/fs/http_client_test.cpp src/paimon/fs/s3/CMakeLists.txt src/paimon/fs/s3/s3_file_system.cpp src/paimon/fs/s3/s3_file_system.h src/paimon/fs/s3/s3_file_system_test.cpp
• cmake --build build --target paimon-http-client-test paimon-s3-file-system-test -j64
• ./build/debug/paimon-http-client-test
• ./build/debug/paimon-s3-file-system-test

API and Format

No public API, storage format, or protocol changes.

Documentation

No.

Generative AI tooling

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