[release] Core stable release 1.15.0 updates#6841

Kielek merged 2 commits intomainopen-telemetry/opentelemetry-dotnet:mainfrom

otelbot/post-stable-core-1.15.0-updateopen-telemetry/opentelemetry-dotnet:otelbot/post-stable-core-1.15.0-updateCopy head branch name to clipboard