Nydus Snapshotter v0.15.12 Release

What's Changed

• [auth] Refactor providers to use AuthProvider interface by @Fricounet in #707
• [auth] Add kubelet credential provider support by @Fricounet in #710
• Add OCI index detection for Nydus alternatives by @Fricounet in #669
• [e2e] Centralize Kubernetes version by @Fricounet in #713
• [snapshot] Reimplement cache GC by @Fricounet in #711
• [auth] Introduce token renewals system by @Fricounet in #714
• add Fricounet as a committer by @imeoer in #715
• [auth] Support token expirations from provider by @Fricounet in #716
• fix(converter): preserve metadata-only layers in nydus manifest by @BraveY in #720

Full Changelog: v0.15.11...v0.15.12