[FEATURE REQ] Extractor and Publisher support for the workspace-level "All APIs" policy

### Please describe the feature.

APIM exposes a workspace-level policy resource (the workspace equivalent of the service-level "All APIs" policy) at `workspaces/{workspaceId}/policies/policy` (ARM type `Microsoft.ApiManagement/service/workspaces/policies`, available since API version `2024-05-01`).

Neither the extractor nor the publisher currently handles this resource type. If a team adds a policy to the workspace's "All APIs" scope in the Azure portal and runs the extractor, no `policy.xml` is written at the workspace root — the resource is silently skipped with no warning, no file, and no PR.

This was noted during the original workspace support planning in #274 (April 2023) but was not included when that issue was closed against the v7 release.