[partition] Make convenienceName() available for debugging

- Function for human-readable names is useful in more parts of
   the partition module.

src/modules/partition/core/PartUtils.h

@@ -46,6 +46,15 @@ enum SizeUnit
     GiB
 };
 
+/**
+ * @brief Provides a nice human-readable name for @p candidate
+ *
+ * The most-specific human-readable name for the partition @p candidate
+ * is returned (e.g. device name, or partition path). In the worst
+ * case, a string representation of (void *)candidate is returned.
+ */
+QString convenienceName( const Partition* const candidate );
+
 /**
  * @brief canBeReplaced checks whether the given Partition satisfies the criteria
  * for replacing it with the new OS.