Add Fleet and Kibana checks in create env workflow

[seanrathier]

Summary of your changes

Adds a Kibana and Fleet readiness check to the CDR composite action, ensuring Fleet Server is fully operational before integration installation scripts run. Previously, integrations were installed immediately after Kibana reported available, causing race conditions where Fleet Server was still initializing.

Root causes addressed:

• `GET /api/fleet/status` returns 404 on ESS deployments — replaced with `POST /api/fleet/setup` (triggers Fleet initialization) followed by stability polling on `GET /api/fleet/epm/packages`
• Fleet Server passes a single readiness check but crashes under load — now requires 5 consecutive 200s before proceeding
• `perform_api_call` only retried 5xx errors — 429 (TLS handshake timeout surfaced as rate limit) and `400 "not available with current configuration"` (Fleet mid-init) are now also retried
• `get_package_version` silently returned `None` on failure, causing 16 install scripts to POST a null package version and receive a confusing `400 "expected string but got null"` — now raises immediately
• `delete_env.sh` jq expression had an operator precedence bug causing `Cannot index string with string "StackName"` when filtering CloudFormation stacks

Files changed:

• `.github/actions/cdr/action.yml` — new "Wait for Kibana and Fleet to be ready" step: Kibana available → `POST /api/fleet/setup` → 5× consecutive `GET /api/fleet/epm/packages` 200; adds `serverless-mode` input to skip the Fleet check on serverless deployments
• `.github/workflows/test-environment.yml` — passes `serverless-mode` through to the CDR action
• `tests/fleet_api/base_call_api.py` — retries 429 and the Fleet-not-ready 400; increases default `max_retries` from 3 to 8 with backoff capped at 30s
• `tests/fleet_api/common_api.py` — `get_package_version` raises on failure instead of returning `None`
• `deploy/test-environments/delete_env.sh` — fixes jq operator precedence bug in CloudFormation stack filtering

Screenshot/Data

Related Issues

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary README/documentation (if appropriate)

Introducing a new rule?

• Generate rule metadata using this script
• Add relevant unit tests
• Generate relevant rule templates using this script, and open a PR in elastic/packages/cloud_security_posture

[mergify]

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

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.