feat: add support for queryTimeout in datasources

[weisdd]

Description

This PR adds support for queryTimeout (part of jsonData) in datasources.

Relevant issues/tickets

Closes: #782

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• This change requires a documentation update
• I have added tests that prove my fix is effective or that my feature works
• I have added a test case that will be used to verify my changes
• Verified independently on a cluster by reviewer

Verification steps

1. Add a datasource with a custom queryTimeout in jsonData:

apiVersion: integreatly.org/v1alpha1
kind: GrafanaDataSource
metadata:
  name: example-grafanadatasource
spec:
  name: middleware.yaml
  datasources:
    - name: Prometheus
      type: prometheus
      access: proxy
      url: http://prometheus-service:9090
      isDefault: true
      version: 1
      editable: true
      jsonData:
        tlsSkipVerify: true
        timeInterval: "5s"
        queryTimeout: 30s

2. In Grafana, inspect the datasource: