test(docker-tests): add end-to-end test for file-based declarative configuration

[ArjunPakhan]

Description

This PR introduces a dedicated end-to-end integration test (test_otel_config_file_e2e) within the Docker test suite to validate the SDK's file-based declarative configuration mechanism.

It ensures that configuring the SDK via the OTEL_CONFIG_FILE environment variable successfully reads, parses, and validates structural schemas against a configuration file (minimal_config.yaml), loads the underlying protocol bindings dynamically, and initializes a functional tracing pipeline.

Changes

• Added tests/opentelemetry-docker-tests/tests/declarative_config/minimal_config.yaml with valid file schema settings mapping to a local OTLP gRPC endpoint.
• Added tests/opentelemetry-docker-tests/tests/declarative_config/test_otel_config_file.py to assert correct SDK instantiation and baseline resource attribution mapping.
• Incorporated explicit provider.shutdown() lifecycle flushing to guarantee background span batches dispatch successfully across network boundaries within rapid test loops.

Testing Strategy

Verified locally inside the docker-test virtual environment against a live running otel-collector container instance:

pytest -s declarative_config/

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ArjunPakhan / name: Arjun Pakhan (0c47bd7)