Fleet and Elastic Agent 8.19.15

IMPORTANT: This documentation is no longer updated. Refer to Elastic's version policy and the latest documentation.

Strip Unit.Config from components diagnostic files to prevent secret leakage. #13338

Retry Elasticsearch requests on TLS handshake errors so multi-host outputs can fail over. #6767
Fix typos in default rate limit YAML keys that prevented PGP retrieval and policy limits from loading. #6835
Persist logging level across agent restarts after policy changes. #13289
Fix graceful shutdown of Beats processes on Windows when Elastic Agent runs as a service. #13581
Fix OpenTelemetry collector configuration to correctly merge user-defined extensions with automatically generated ones. #13639