[Azure] SkyPilot provisioner for Azure

[Michaelvll]

Blocked by #3696, #3700

Single-node (similar to #3697)

multitime -n 5 sky launch --cloud azure -y --cpus 2
            Mean        Std.Dev.    Min         Median      Max
real        228.265     17.847      200.288     227.464     256.668
user        5.712       0.412       5.415       5.524       6.526
sys         1.375       0.042       1.322       1.372       1.438

Single-node launch on existing cluster

Multi-node (2.24x speed up than #3697)

multitime -n 5 sky launch --cloud azure -y --cpus 2 --num-nodes 2
            Mean        Std.Dev.    Min         Median      Max
real        241.430     16.028      221.751     244.685     266.587
user        5.712       0.141       5.535       5.682       5.913
sys         1.448       0.028       1.397       1.447       1.479

TODO:

• Backward compatibility (especially check: actual name starting ray- vs sky- and changing the name of deployment from ray-config to skypilot-config)
• Adding head and worker in the name of instances

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: conda deactivate; bash -i tests/backward_compatibility_tests.sh