feat: Trigger warning for PRs likely requiring updates to management-plane-charts

[medmes]

Description

This PR introduce a Github wokflow for detecting changes on the config directory which needs to be reflected into management-plane-chart repository.

Changes proposed in this pull request:

• Github Workflow.

The PR was tested against this Upsttream PR in order to bypass permission complexity:

#2223

For the PR merger
After the Pull request is merged. Please delete the trigger_warning_job_on_pr branch from the upstream.

Related issue(s)
#2089

[c-pius]

Overall looks good, just some general suggestions:

• I think I would split this into two workflows, one verifying that manifests are up to date, one checking if there are relevant changes
• regarding the config changes, I think it would be more robust if we work on the actual output based on the configuration
  • so instead of checking if there are changes on the config files, I would suggest that we generate the KLM manifests from PR and main and compare if there are changes
  • we already did this in an earlier implementation that can be used as a base again: chore: Verify diff in manifests #1358
• the previous point will cover the configuration part, but the ticket also says that the e2e test files are relevant. Here I don't think that we have output to work on, so an approach where we just look if there is a diff in the files should be sufficient. The GH actions and scripts part should be the most relevant. Also, on top level the scripts/tests part should be included in the check.
• I personally prefer consistency in approaches whenever possible. Here, we have multiple cases where we share info between different steps. First, we use the outputs of the previous steps, later, we use env variables. I would suggest to consistently use outputs in this case.