Declarative configuration is stable!

Key parts of the OpenTelemetry declarative configuration specification have reached stable status, including the data model (JSON & YAML), parsing mechanisms, and a standard environment variable for config file paths. This stability, with implementations already available in five languages and more underway, will allow for consistent OpenTelemetry configuration across different languages and a richer set of options beyond environment variables. The project now focuses on expanding the schema, encouraging wider language implementation, and eventually deprecating less interoperable environment variable configurations.