Fix Scoop shim failure under RedirectionGuard by retrying elevated

[Gabriel Dufresne (GabrielDuf)]

This pull request improves how the Scoop package manager handles shim creation failures that require elevation, and adds tests to ensure this behavior works as expected. The main change is to automatically retry failed shim operations with elevated privileges if a specific error is detected, preventing unnecessary failures and improving reliability.

Scoop shim error handling:

• Updated ScoopPkgOperationHelper.cs to detect shim resolution failures (messages containing "Can't shim") and automatically retry the operation with elevated privileges, unless already running as administrator. This prevents failures caused by permission issues when creating shims.

Test coverage improvements:

• Added unit tests in ScoopManagerTests.cs to verify:
  • The operation is retried with elevation on shim resolution failure, and does not loop if already elevated.
  • The presence of a "Can't shim" message does not trigger a retry if the operation succeeded.