Fix: Allow credential files with the same basename.

[concretevitamin]

With OCI supported and enabled, I encountered the following error on every sky launch:

...
  File "/Users/zongheng/Dropbox/workspace/riselab/sky-computing/sky/backends/backend_utils.py", line 975, in write_cluster_config
    _optimize_file_mounts(tmp_yaml_path)
  File "/Users/zongheng/Dropbox/workspace/riselab/sky-computing/sky/backends/backend_utils.py", line 228, in _optimize_file_mounts
    f'Duplicated src basename: {src_basename}; mounts: {file_mounts}')
AssertionError: Duplicated src basename: config; mounts: {'~/.sky/sky_ray.yml': '/Users/zongheng/.sky/generated/sky-0fe1-zongheng.yml.tmp', '~/.sky/wheels/4ae6677e0222ae99e0d7c13323ab1f16': '/var/folders/8f/56gzvwkd3n3293xjlrztr6600000gp/T/4ae6677e0222ae99e0d7c13323ab1f16', '~/.aws/credentials': '~/.aws/credentials', '~/.azure/azureProfile.json': '~/.azure/azureProfile.json', '~/.azure/clouds.config': '~/.azure/clouds.config', '~/.azure/config': '~/.azure/config', '~/.azure/msal_token_cache.json': '~/.azure/msal_token_cache.json', '~/.config/gcloud/credentials.db': '~/.config/gcloud/credentials.db', '~/.config/gcloud/application_default_credentials.json': '~/.config/gcloud/application_default_credentials.json', '~/.config/gcloud/access_tokens.db': '~/.config/gcloud/access_tokens.db', '~/.config/gcloud/configurations': '~/.config/gcloud/configurations', '~/.config/gcloud/legacy_credentials': '~/.config/gcloud/legacy_credentials', '~/.config/gcloud/active_config': '~/.config/gcloud/active_config', '~/.sky/.sky_gcp_config_default': '~/.sky/.sky_gcp_config_default', '~/.lambda_cloud/lambda_keys': '~/.lambda_cloud/lambda_keys', '~/.ibm/credentials.yaml': '~/.ibm/credentials.yaml', '~/.oci/config': '~/.oci/config', '~/.oci/oracleidentitycloudservice_gengming.chen-06-06-05-01.pem': '~/.oci/oracleidentitycloudservice_gengming.chen-06-06-05-01.pem', '~/.ssh/sky-key.pub': '~/.ssh/sky-key.pub'}

The root cause is because both ~/.oci/config and ~/.azure/config exist locally, and our previous file_mounts optimization couldn't handle basename conflicts.

Fixed by using uuids as basename when doing the file_mounts optimization.

Tested (run the relevant ones):

• Any manual or new tests for this PR (please specify below)
• All smoke tests: pytest tests/test_smoke.py: running
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: bash tests/backward_comaptibility_tests.sh

[Michaelvll]

Thanks for fixing this @concretevitamin! LGTM.

[concretevitamin]

Smoke tests passed*, merging.

*Re-tried pytest tests/test_smoke.py::test_large_job_queue once. The first time it failed at

[large_job_queue] Failed.
[large_job_queue] Reason: s=$(sky queue t-large-job-queue-3917-e7); echo "$s"; echo; echo; echo "$s" | grep -v grep | grep PENDING | wc -l | grep 43

with the grep count being incorrect. Is it expected?