Build Overview and Pipeline dashboards for Logstash OTel metrics

[estolfo]

Build the following dashboards using the Logstash metrics sent via OTLP:

• Logstash Overview
• Pipelines Overview
• Pipeline Details Overview

[estolfo]

Note the limitations:

Pipelines Overview

Worker Utilization

uses logstash.pipeline.total.flow.worker_utilization.last_1_minute, a flow rate metric

The current value might be able to be used instead, will investigate the difference.

[estolfo]

Logstash Overview:

[estolfo]

Pipelines Overview:
Worker Utilizaton just uses the current, scalar value (see limitations comment above)