fix(6023): replace list with items

[kaanyalti]

• Bug

What does this PR do?

Replaces list with items from from kibanaFetchToken as the list is deprecated in the api response and will be removed.

Why is it important?

The list in the api response is going to be removed in favor of item

Checklist

• My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files
• [ ] I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

There shouldn't be any user impact

How to test this PR locally

• Deploy ESS
• Build the agent by running the following command

SNAPSHOT=true PLATFORMS="linux/arm64" PACKAGES="docker" EXTERNAL=true mage -v package

• Then get the image id for any of the created elastic-agent images and run the following command

docker run \
  --env FLEET_ENROLL=1 \
  --env KIBANA_HOST=<KIBANA HOST> \
  --env KIBANA_USERNAME=<KIBANA USER NAME> \
  --env KIBANA_PASSWORD=<KIBANA PASSWORD> \
  --env FLEET_TOKEN_POLICY_NAME=<POLICY NAME> \
  --env FLEET_URL=<FLEET URL> \
  --rm <IMAGE ID>

• Validate that the agent is able to enroll

Related issues

• Closes Fleet deprecated list property when retrieving enrollment api keys #6023

[mergify]

This pull request does not have a backport label. Could you fix it @kaanyalti? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-v8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[kaanyalti]

I would like to add an issue link to remove the link from the kibana api, if anyone knows of such an issue please comment here.

[elastic-sonarqube]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 40%)

See analysis details on SonarQube