[Core][Docker] Support docker login on RunPod.

[cblmemo]

Fixes #4269.

TO DISCUSS:

Currently RunPod Python API does not provide enough API to delete the template, so we manually call the graphql api instead. Also, this PR adds a ephemeral_resources to the provision records for all resources generated from launching process. I've requested those features in the RunPod python sdk repo: runpod/runpod-python#390

Sometimes the deletion of registry auth will fail without a clear error message. Cleanup of template is always successful though. I also submitted this: runpod/runpod-python#391

$ sky down rp-docc-3
Terminating 1 cluster: rp-docc-3. Proceed? [Y/n]: 
Terminating 1 cluster ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━   0% -:--:--{'errors': [{'message': 'Something went wrong. Please try again later or contact support.', 'path': ['deleteRegistryAuth'], 'extensions': {'code': 'INTERNAL_SERVER_ERROR'}}], 'data': {'deleteRegistryAuth': None}}
Failed to delete registry auth cm56jeayk0001l208aehw3oe9: Something went wrong. Please try again later or contact support.Please delete it manually.
Terminating cluster rp-docc-3...done.
Terminating 1 cluster ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)

# @temp/rp_docker.yaml
resources:
  cloud: runpod
  image_id: docker:txia-test-ecr:latest

envs:
  SKYPILOT_DOCKER_USERNAME: AWS
  SKYPILOT_DOCKER_PASSWORD:
  SKYPILOT_DOCKER_SERVER: 679991763071.dkr.ecr.us-east-1.amazonaws.com

run: which nginx

$ SKYPILOT_DOCKER_PASSWORD=$(aws ecr get-login-password --region us-east-1) sky launch @temp/rp_docker.yaml -c rp-doc --env SKYPILOT_DOCKER_PASSWORD 'which nginx'
⚙︎ Launching on RunPod NL.
└── Instance is up.
✓ Cluster launched: rp-doc.  View logs at: ~/sky_logs/sky-2024-12-27-00-10-55-296823/provision.log
⚙︎ Mounting files.
⚙︎ Job submitted, ID: 1
├── Waiting for task resources on 1 node.
└── Job started. Streaming logs... (Ctrl-C to exit log streaming; job will not be killed)
(task, pid=2396) /usr/sbin/nginx
✓ Job finished (status: SUCCEEDED).

• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: conda deactivate; bash -i tests/backward_compatibility_tests.sh

[cblmemo]

Maybe they are including the server name in the image name.

[cblmemo]

@Michaelvll This is ready for a review!