Update data folder migration for spaces in plugin names. Fixes BUKKIT-5417

This change drops the previous plugin data folder migration based on the
plugin's file name, and adapts the migration to now instead consider
plugins that have spaces in their original name.

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/main/java/org/bukkit/plugin/PluginDescriptionFile.java

@@ -1005,4 +1005,12 @@ public final class PluginDescriptionFile {
         }
         throw new InvalidDescriptionException(object + " is not properly structured.");
     }
+
+    /**
+     * @deprecated Internal use
+     */
+    @Deprecated
+    public String getRawName() {
+        return rawName;
+    }
 }