[Logstash]: Add rule templates and slo templates to Logstash integration to improve enterprise-readiness

### Integration Name

Logstash [logstash]

### Dataset Name

logstash.*

### Integration Version

2.10.x

### Agent Version

9.3.3

### OS Version and Architecture

N/A

### User Goal

Monitor Logstash effectively via meaningful pre-configured Rule Templates and SLO Templates.

Some (non-exaustive) Ideas:

- Persistent Queue Fullness
- Memory Queue Fullness (the data is not generated yet by Logstash)
- Worker Utilization higher than x% for y time
- System Load 5m / 15m higher than threshold
- Health Report red/yellow for certain amount of time
- Failure reload of pipeline
- Logstash stopped (from the logs)
- Logstash OOM (from the logs)
- Nuber of Threads higher than threshold
- Open File Descriptors higher than threashold
- GeoIP database expiration

### Existing Features

The current version of the integration does not provide any rule template and slo template.

### What did you see?

NA

### Anything else?

To implement this we need to:

1. Bump the version of the Logstash integration package-spec to an appropriate version >3.5.x
2. Identify appropriate alert scenarios
3. Identify appropriate SLO scenarios
4. Implement scenarios