test: add upload/download instance method and UploadFileResult branch tests

Add 11 new test classes covering OswExpress.upload_file/download_file
instance methods, UploadFileResult branches (LFC source, URL domain
extraction, env var domain, target_fpt meta/change_id, osw_express from
source controller, invalid source type), and import_with_fallback wiki
fallback path. Fix bug in upload_file() where locals() caused duplicate
keyword args. Coverage for express.py increased from 79% to 90%.

Author: LukasGold

src/osw/express.py

@@ -307,6 +307,9 @@ def upload_file(
         """
         # Preparing all args, kwargs & properties to set for the uploaded file
         data = {**locals(), **properties}
+        # Remove 'self', 'source', and 'properties' to avoid duplicate keyword args
+        for key in ("self", "source", "properties"):
+            data.pop(key, None)
         # Clean data dict to avoid passing None values
         data = {key: value for key, value in data.items() if value is not None}
         # Make sure self is passed as osw_express