[Volume] Improve log and add alias for volumes

[DanielZhangQD]

• Improve log for creating and deleting volumes in k8s
• Add alias sky volume for sky volumes

Tested (run the relevant ones):

• Code formatting: install pre-commit (auto-check on commit) or bash format.sh
• Any manual or new tests for this PR (please specify below)

✗ sky volume apply -y -n pvc1 --type k8s-pvc --size 2GB --infra k8s
Created PVC pvc1-43dbb4ab-481fd3 in namespace default
✗ sky volume delete pvc1
Deleting 1 volume: pvc1. Proceed? [Y/n]:
Deleted PVC pvc1-43dbb4ab-481fd3 in namespace default

• All smoke tests: /smoke-test (CI) or pytest tests/test_smoke.py (local)
• Relevant individual tests: /smoke-test -k test_name (CI) or pytest tests/test_smoke.py::test_name (local)
• Backward compatibility: /quicktest-core (CI) or pytest tests/smoke_tests/test_backward_compat.py (local)

[aylei]

LGTM, thanks!