Validate that the durations in ILM and lifecyle.yml are the same

Context
With the addition of serverless, a DLM (data_stream//lifecycle.yml) file was added to define data retention. Packages may also have an data_stream//elasticsearch/ilm/default_policy.json file that defines data retention for non-serverless deployments. We have at least integration where a PR updated the duration in one of the files, but not the other.

Business Case
Users are sensitive to changes in behavior when they upgrade or move their integrations. A change in data retention between serverless and non serverless deployments will create differences in storage size that the users may note and want an explanation for. Syncing durations will keep SDHs from being created to explain the difference.

Requested New Requirement
Add a check in "elastic-package check" to validate that the durations in the files match when both files exist.

Start with the "elastic-package check" command and inspect data_stream//lifecycle.yml alongside data_stream//elasticsearch/ilm/default_policy.json when both exist. Add validation that their data-retention durations match, then verify that the check reports a mismatch and accepts matching durations.

Written by the indexing model from the issue text.