with HELM_DIFF_USE_UPGRADE_DRY_RUN=true helm-diff only parses MANIFEST section missing the HOOKS

related to @mumoshu comment https://github.com/databus23/helm-diff/issues/358#issuecomment-1020657732

> Ah, gotcha! helm-diff currently parses MANIFEST section of helm upgrade --dry-run only so that's why helm diff upgrade with the three-way-merge option is missing the entire hooks from the diff. Sounds like it worth a dedicated github issue.