Define stability guarantees for stable releases

[jack-berg]

trafficstars

Fill in the details of the TODOs: https://github.com/open-telemetry/opentelemetry-configuration?tab=readme-ov-file#stability-definition

Should look to the opentelemetry-proto stability guarantees for guidance / prior art.

Need to find a way to have experimental portions of config even after the schema is stable overall, similar to how proto has experimental profile signal while logs, metrics, and traces are stable.

[codeboten]

Related to https://github.com/open-telemetry/opentelemetry-configuration/issues/2