Support OTEL based Metrics Index Mapping in place

[YANG-DB]

Is your feature request related to a problem?

similar to traces the Observability Metrics mapping should be defined under the Observability plugin

Currently Observability has no notion or index to hold the Metrics signals as defined by the OTEL standard.
In correlation with the schema definition for traces the metrics will also be explicitly defined and supported by Observability plugin.

This includes:

• Index structure (mapping)
• Index naming convention
• Json schema for enforcement and validation of the structure

What solution would you like?
Move the structure and naming from the ingestion to the core Observability

This would simply next use cases:

• allow 3rd party ingestion developers to have a consolidated location to retrieve and validate their Observability schema
  • Fluent-D
  • Jaeger
• Allow the development of a pre-defined Observability dashboards that know and project the metrics structure

Simplify any ingestion framework lifecycle by not having to maintain or care about the lifecycle of the target index to populate

What alternatives have you considered?
N/A

Do you have any additional context?

• Support OTEL based Trace Index Mapping in place #1388
• [FEATURE] Add support to display Data Prepper metrics  #1383
• https://github.com/opensearch-project/data-prepper/tree/main/data-prepper-plugins/otel-metrics-source