[UX] Make sky check more fine-grained for GCP

[Michaelvll]

Fixes #2184

This PR makes the sky check provides information based on the status of the user's current setup.

Missing dependency:

$ sky check
Checking credentials to enable clouds for SkyPilot.
  AWS: enabled          
  Azure: enabled          
  GCP: disabled          
    Reason: GCP tools are not installed. Run the following commands:
      $ pip install google-api-python-client
      $ conda install -c conda-forge google-cloud-sdk -y
    Credentials may also need to be set. Run the following commands:
      $ gcloud init
      $ gcloud auth application-default login
    For more info: https://skypilot.readthedocs.io/en/latest/getting-started/installation.html#google-cloud-platform-gcp
    Details: [builtins.ModuleNotFoundError] No module named 'googleapiclient'
  Lambda: enabled          
  IBM: enabled          
  SCP: enabled          
  OCI: enabled          
  Cloudflare (for R2 object store): enabled          

SkyPilot will use only the enabled clouds to run tasks. To change this, configure cloud credentials, and run sky check.

Without gcloud init:

$ sky check                   
Checking credentials to enable clouds for SkyPilot.
  AWS: enabled          
  Azure: enabled          
  GCP: disabled          
    Reason: Credentails are not set. Run the following commands:
      $ gcloud init
      $ gcloud auth application-default login
    For more info: https://skypilot.readthedocs.io/en/latest/getting-started/installation.html#google-cloud-platform-gcp
    Details: [builtins.FileNotFoundError] ~/.config/gcloud/access_tokens.db
  Lambda: enabled          
  IBM: enabled          
  SCP: enabled          
  OCI: enabled          
  Cloudflare (for R2 object store): enabled          

SkyPilot will use only the enabled clouds to run tasks. To change this, configure cloud credentials, and run sky check.
If any problems remain, please file an issue at https://github.com/skypilot-org/skypilot/issues/new

Without gcloud auth application-default login:

$ sky check
Checking credentials to enable clouds for SkyPilot.
  AWS: enabled          
  Azure: enabled          
  GCP: disabled          
    Reason: Application credentials are not set. Run the following commands:
      $ gcloud auth application-default login
    Or set the environment variable GOOGLE_APPLICATION_CREDENTIALS to the path of your service account key file.
    For more info: https://skypilot.readthedocs.io/en/latest/getting-started/installation.html#google-cloud-platform-gcp
    Details: [builtins.FileNotFoundError] ~/.config/gcloud/application_default_credentials.json
  Lambda: enabled          
  IBM: enabled          
  SCP: enabled          
  OCI: enabled          
  Cloudflare (for R2 object store): enabled          

SkyPilot will use only the enabled clouds to run tasks. To change this, configure cloud credentials, and run sky check.
If any problems remain, please file an issue at https://github.com/skypilot-org/skypilot/issues/new

Tested (run the relevant ones):

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

[concretevitamin]

Thanks a bunch @Michaelvll! One minor nit.

[concretevitamin]

Can we also hint the CLI commands that are equivalent to L571 & 574? Something like "Getting project ID / current user failed. You can debug with "cmd1" and "cmd2". {_CREDENTIAL_HINT}"

[Michaelvll]

Good point! Added. There is no exactly equivalent command for auth.default(), but this exception is a very rare case, if the previous checks pass. We only add the gcloud auth list command here, and can wait for more feedbacks if user encounter this issue. : )