Fix remaining tag references in tests

- Update CacheRequest test to use version field
- Fix upload_test_file calls that still used tag parameter
- Update artifact history test to check versions instead of tags
- Update artifact stats tests to check versions instead of tags
- Fix garbage collection tests to delete versions instead of tags
- Remove TestGlobalTags class (endpoint removed)
- Update project/package stats tests to check version_count
- Fix upload_test_file fixture in test_download_verification

backend/tests/test_download_verification.py

@@ -29,13 +29,13 @@ def upload_test_file(integration_client):
         artifact_id = upload_test_file(project, package, content, version="v1.0")
     """
 
-    def _upload(project_name: str, package_name: str, content: bytes, tag: str = None):
+    def _upload(project_name: str, package_name: str, content: bytes, version: str = None):
         files = {
             "file": ("test-file.bin", io.BytesIO(content), "application/octet-stream")
         }
         data = {}
-        if tag:
-            data["tag"] = tag
+        if version:
+            data["version"] = version
 
         response = integration_client.post(
             f"/api/v1/project/{project_name}/{package_name}/upload",