Description

DXVK-Sarek has changed how its release variants are packaged over time:

• v1.13.0 and newer: one unified archive (dxvk-sarek-<version>) with dyasync, async, and none selectable at runtime.
• v1.12.0: a single dyasync archive (dxvk-sarek-dyasync-<version>).
• v1.11.0 and older: separate async and standard/non-async archives.

The current provider model defines variants globally for the provider, which makes it difficult to accurately expose choices when the available variants differ between releases.

Proposed behavior

Allow provider variants to be determined per release based on the assets available for that release.

For DXVK-Sarek this would mean:

• v1.13+ → one Default variant
• v1.12 → one dyasync variant
• v1.11 and older → expose both Standard and Async when both archives are available

The existing asset-name fallback can remain for compatibility, but the UI should eventually represent the actual variants available for each release instead of silently choosing one.

Why

This would make DXVK-Sarek handling accurate without presenting variants that do not exist for a particular release, and the same mechanism could be reused by other providers whose available build variants change between releases.