Add Observability Schema Support [FEATURE]

[YANG-DB]

Is your feature request related to a problem?
As the observability domain continue to evolve - we are facing a concrete need of organizing the telemetry data into a structured data-model layer.

This data model layer needs to serves as a bridge between the telemetry collecting and visualization. It matters for both developers and users of these components to agree on a uniform data model. Another goal is to understand the role data models plays in observability and what kind of data model required in our case.

Uniform data model, such as ECS and OpenTelemetry, provides the following benefits:

1. Normalization: normalize event data in uniform format
2. Correlation: correlate between logs, metrics and traces
3. Simplified search: filter and aggregate across different events easily
4. Unified visualization: make pre-canned dashboards possible
5. Field name recall and deduction: by single set and same convention

What solution would you like?
Create a draft for opensearch observability schema supporting the following domains:

• Log schema
• Trace schema
• Metrics Schema

What alternatives have you considered?
Existing alternatives are for example:

• Elastic Common Schema (https://github.com/elastic/ecs)
• Open Telemetry Schema (https://opentelemetry.io/docs/reference/specification/schemas/overview/)
• Cloud event Schema (https://github.com/cloudevents/spec)

See RFC #763

[YANG-DB]

issue moved to the observability project