Add concurrent chunked uploads to SDKs

[TorstenDittmann]

Summary

• Upload the first chunk serially to establish the upload ID, then upload remaining chunks concurrently across SDK upload implementations.
• Use a max concurrency of 8 while preserving upload progress callbacks and resume behavior where supported.
• Remove the empty root package lock file.

Updated SDK templates

• Web, Node, React Native
• PHP, Ruby, Python
• Dart, Flutter
• Go, Swift, Apple, DotNet
• Android, Kotlin
• Rust, Deno templates

Verification

• Regenerated affected supported examples with php example.php <sdk>.
• Ran composer lint-twig.
• Ran npm run build:types in examples/web.
• Ran Python, Ruby, and PHP syntax checks for generated clients.
• Attempted containerized PHPUnit with docker run --rm -v $(pwd):$(pwd):rw -w $(pwd) php:8.3-cli-alpine vendor/bin/phpunit; blocked because the PHP container does not include the Docker CLI used by the SDK tests.
• Attempted local vendor/bin/phpunit; blocked in Android SDK tests by Gradle/JDK image issues (android-34-jdk11 has JDK 11 but the Android Gradle plugin requires Java 17) and ARM host vs amd64 image file-watcher errors.

Notes

• Docker is available locally, but the full PHPUnit SDK suite currently requires additional Android/Docker environment fixes before it can complete on this machine.
• Some full generated SDK builds/analyzers still fail on pre-existing generated model/dependency issues unrelated to upload changes.