Use all available RunPod regions by default

[jvstme]

Current

The RunPod backend only uses a fixed set of regions by default.

REGIONS = [
    "CA-MTL-1",
    "EU-NL-1",
    "EU-RO-1",
    "EU-SE-1",
    "EUR-IS-1",
    "EUR-IS-2",
    "EUR-NO-1",
    "US-OR-1",
]

This leads to poorer GPUs availability, e.g. NVIDIA H100 NVL (94GB) is only available in US-KS-2 that is not used by default.

Proposed

Allow using all existing regions unless a specific set of regions is configured in .dstack/server/config.yml.

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[r4victor]

Note that the fix introduced in #1757 requires the backend config to be updated to use all regions.