DBAAS: Include Additional Metrics OpenSearch + MySQL

[dwilsondo]

Adds metrics for DBAAS services (OS, MySQL), see full list of metrics in whitelist.go. Broadly includes:

• OS cluster health
• OS cluster stats (e.g. total documents)
• OS JVM usage
• OS indices requests + timing
• OS HTTP API stats
• MySQL Replication Lag

The OS metrics use multiple exporters for different subsystems. To handle this we drop redundant node and cluster identifiers from each section as needed (see aggregation.go). Tested locally w. sample OpenSearch metrics served via an HTTP server on 127.0.0.1:9273. As expected, OS metrics are available and redundant identifiers e.g. node_host (duplicates node_name) and cluster_name (prefer dbaas_uuid in practice) are dropped.

go run . --stdout-only --dbaas-metrics-path http://127.0.0.1:9273/os.txt

[opensearch_indices_search_query_time_in_millis]: map[__name__:opensearch_indices_search_query_time_in_millis cloud:custom-digitalocean-do-nyc3 host:os-test-2 node_attribute_shard_indexing_pressure_enabled:true node_id:3NI_MJsoQiOEN-kOc4S-zQ node_name:os-test-2 node_roles:data,ingest,master,remote_cluster_client service:os-test service_type:opensearch]: 5857
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