Add Grafana/Prometheus auth functionality

• Add new Grafana/Prometheus password creations
• Change ${CI_BUILDS_DIR}/${CI_PROJECT_PATH} to ${CI_PROJECT_DIR} variable
• Change 'validate_cluster' to use cached kubeconfig from 'configure:secrets' (the same way as Helmfile uses it)
• Add 'retry' 1 time if failed Helmfile job

Tests:

• Existing cluster (Gitlab Internal): https://gitlab-internal.builder.ai/devsecops/team/davidpv/davidpv-platform/-/pipelines/146533
• New cluster (Gitlab Internal): https://gitlab-internal.builder.ai/devsecops/team/davidpv/davidpv-platform-test/-/pipelines/146539
• New cluster (Gitlab External): https://gitlab.builder.ai/devsecops/davidpv/davidpv-platform-external/-/pipelines/12124993