UX: Allow inferring cloud from region or zone.

[concretevitamin]

Fixes #1882. Also, unregisters Local cloud, which is done to provide good 1-cloud hints.

Tested (added to unit tests too) with all clouds enabled incl. k8s:

OK cases:

# Maps to GCP.
» sky launch --region us-east1
» sky launch --zone us-west2-a

# Maps to AWS.
» sky launch --region us-east-2
» sky launch --zone us-west-2a

# OK: Optimizer prints.
» sky launch
» sky launch --region us-east-1 --cloud aws
» sky launch --region us-east-1 --cloud lambda

Not OK cases:

» sky launch --region us-east-1
ValueError: Cannot infer cloud from (region 'us-east-1', zone None). Multiple enabled clouds have region/zone of the same names: [AWS, Lambda]. To fix: explicitly specify `cloud`.

» sky launch --zone us-west-2-a --cloud aws
ValueError: Invalid zone 'us-west-2-a'
Did you mean one of these: 'us-west-2a'?

» sky launch --zone us-west-2-a                                            
ValueError: Invalid (region None, zone 'us-west-2-a') for any cloud among [AWS, Azure, GCP, IBM, Kubernetes, Lambda, OCI, SCP]. Details:
Cloud       Hint
-----       ----
AWS         Invalid zone 'us-west-2-a' Did you mean one of these: 'us-west-2a'?
Azure       Azure does not support zones.
GCP         Invalid zone 'us-west-2-a' Did you mean one of these: 'us-west2-a'?
IBM         Invalid zone 'us-west-2-a'
Kubernetes  Kubernetes support does not support setting region. Cluster used is determined
            by the kubeconfig.
Lambda      Lambda Cloud does not support zones.
OCI         Invalid zone 'us-west-2-a'
SCP         SCP Cloud does not support zones.

» sky launch --zone us-west-2z
ValueError: Invalid (region None, zone 'us-west-2z') for any cloud among [AWS, Azure, GCP, IBM, Kubernetes, Lambda, OCI, SCP]. Details:
Cloud       Hint
-----       ----
AWS         Invalid zone 'us-west-2z' Did you mean one of these: 'us-west-2a, us-west-2b,
            us-west-2c, us-west-2d'?
Azure       Azure does not support zones.
GCP         Invalid zone 'us-west-2z'
IBM         Invalid zone 'us-west-2z'
Kubernetes  Kubernetes support does not support setting region. Cluster used is determined
            by the kubeconfig.
Lambda      Lambda Cloud does not support zones.
Local       Local cloud does not support zones.
OCI         Invalid zone 'us-west-2z'
SCP         SCP Cloud does not support zones.


» sky launch --region us-east1 --zone us-west2-a                         
ValueError: Invalid (region 'us-east1', zone 'us-west2-a') for any cloud among [AWS, Azure, GCP, IBM, Kubernetes, Lambda, OCI, SCP]. Details:
Cloud       Hint
-----       ----
AWS         Invalid region 'us-east1' Did you mean one of these: 'us-east-1'?
Azure       Azure does not support zones.
GCP         Invalid zone 'us-west2-a' for region 'us-east1'
IBM         Invalid region 'us-east1' Did you mean one of these: 'us-east'?
Kubernetes  Kubernetes support does not support setting region. Cluster used is determined
            by the kubeconfig.
Lambda      Lambda Cloud does not support zones.
OCI         Invalid region 'us-east1' List of supported oci regions: 'us-sanjose-1'
SCP         SCP Cloud does not support zones.

In docker, with AWS enabled only:

• TODO: improve on this output, 1-cloud only situations should not need the verbose table

# OK
» sky launch --region us-east-1

» sky launch --zone us-west-2-a
ValueError: Invalid (region None, zone 'us-west-2-a') for cloud AWS. Details:
Invalid zone 'us-west-2-a'
Did you mean one of these: 'us-west-2a'?

» sky launch --region us-east1 --zone us-west2-a
ValueError: Invalid (region 'us-east1', zone 'us-west2-a') for cloud AWS. Details:
Invalid region 'us-east1'
Did you mean one of these: 'us-east-1'?

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

[Michaelvll]

Thanks for adding this functionality @concretevitamin! LGTM.

[Michaelvll]

Nice!

[concretevitamin]

PTAL @Michaelvll, main changes since last review are: better 1-cloud hints, and test fixtures refactoring.

[Michaelvll]

Nice! Thanks for the refactoring of the tests @concretevitamin! LGTM.