Support line chart for DORA charts

What does this MR do and why?

This MR adds the option to specify line chart for the DORA metrics within the Insights feature.

Example definition:

dora:
  title: DORA4
  charts:
    - title: Deployment frequency
      description: Deployment frequency is the frequency of successful deployments to production (hourly, daily, weekly, monthly, or yearly). This measures how often you deliver value to end users. A higher deployment frequency means you can get feedback sooner and iterate faster to deliver improvements and features.
      type: line
      query:
        data_source: dora
        params:
          metric: deployment_frequency
          group_by: day
          period_limit: 90

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #354805 (closed)