[Altren]

The CI workflows still select clear;x-gha,readwrite, but vcpkg has removed the x-gha backend. They therefore rebuild dependencies without the intended binary cache. A recent macOS job also failed downloading gflags because vcpkg did not retry a DNS error.

Use a shared setup action for Linux, macOS, and both Windows jobs:

• Persist vcpkg's filesystem binary cache with actions/cache, separating matrix configurations and runner images. Include the vcpkg revision and dependency configuration in the key, with a fallback to older caches that vcpkg checks for ABI compatibility.
• Add two curl retries with a 10-second delay and a 30-second connection timeout through vcpkg's x-script asset hook. This includes DNS errors and retries individual downloads; compilation and tests are unchanged. vcpkg's normal download fallback and checksum validation remain enabled.
• Remove the obsolete cache URL/token export steps. No additional credentials or repository settings are needed.

[liuzicheng1987]

@Altren thanks for the contribution.