[FEATURE] System Index for Root Cause Analyzer Metrics in OpenSearch

[ansjcy]

Is your feature request related to a problem? Our primary objective is to extend the utility of the PA (Performance Analyzer) and Root Cause Analyzer (RCA) metrics beyond local storage and autotune. Currently, RCA solely sends metrics to a local SQLite database, primarily for downstream autotune recommendations. However, these metrics hold significant value for OpenSearch users seeking to gain insights into system performance.

What solution would you like? To address this, we propose enabling RCA to send metrics to the OpenSearch cluster as a dedicated "system index." This enhancement will provide users with the capability to query and utilize these metrics, even when autotune recommendations are not required.

What alternatives have you considered? A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context? Add any other context or screenshots about the feature request here.