Add host-side compose TDX E2E suite

[kvinwang]

Summary

• add a Docker Compose full-stack E2E suite under test-suites/full-stack-compose
• run KMS and Gateway as host-side services, matching the tdxlab/dstack-k8s compose deployment model
• launch only the real app CVM through VMM/QEMU, with kms_enabled=true and gateway_enabled=true
• include mock Cloudflare DNS API + Pebble ACME for Gateway wildcard certificate issuance
• make Gateway bootstrap script configurable for local ACME/Cloudflare mock endpoints
• avoid gramine-sgx-gen-private-key in the local key provider build by generating the Gramine signing key with OpenSSL

Validation

Ran the real TDX E2E suite successfully:

Gateway wildcard certificate is active
app: status=running progress=done
Gateway -> app HTTP check passed
E2E success

Command used:

sudo su kvin -c "cd /home/kvin/src/meta-dstack/dstack/test-suites/full-stack-compose && DOCKER_BUILDKIT=0 docker compose --env-file .env -f compose.yml up --build --abort-on-container-exit runner"