Add earlier trigger for world migration delay in vanilla logic

paper-server/patches/sources/net/minecraft/server/Main.java.patch

@@ -117,9 +117,11 @@
              LevelStorageSource levelStorageSource = LevelStorageSource.createDefault(universePath.toPath());
              LevelStorageSource.LevelStorageAccess access = levelStorageSource.validateAndCreateAccess(levelName);
              Dynamic<?> levelDataTag;
-@@ -150,12 +_,36 @@
+@@ -149,13 +_,38 @@
+             } else {
                  levelDataTag = null;
              }
++            io.papermc.paper.world.migration.WorldFolderMigration.didInitialLoad = true; // Paper
 
 -            boolean safeModeEnabled = options.has(safeMode);
 +            boolean safeModeEnabled = options.has("safeMode"); // CraftBukkit

paper-server/patches/sources/net/minecraft/util/filefix/FileFixerUpper.java.patch

@@ -0,0 +1,10 @@
+--- a/net/minecraft/util/filefix/FileFixerUpper.java
++++ b/net/minecraft/util/filefix/FileFixerUpper.java
+@@ -82,6 +_,7 @@
+     ) throws FileFixException {
+         int loadedVersion = NbtUtils.getDataVersion(levelDataTag);
+         if (this.requiresFileFixing(loadedVersion)) {
++            if (!io.papermc.paper.world.migration.WorldFolderMigration.didInitialLoad) io.papermc.paper.world.migration.WorldFolderMigration.warnAndDelayStartupMigration(); // Paper
+             LOGGER.info("Starting upgrade for world \"{}\"", worldAccess.getLevelId());
+             Path worldFolder = worldAccess.getLevelDirectory().path();
+             Path fileFixDirectory = worldFolder.resolve("filefix");

paper-server/src/main/java/io/papermc/paper/world/migration/WorldFolderMigration.java

@@ -20,6 +20,7 @@
 public final class WorldFolderMigration {
     private static final Logger LOGGER = LogUtils.getClassLogger();
     private static final boolean DISABLE_MIGRATION_DELAY = Boolean.getBoolean("paper.disableMigrationDelay");
+    public static boolean didInitialLoad;
     private static boolean startupMigrationWarningShown;
 
     private WorldFolderMigration() {
@@ -60,7 +61,7 @@ public static void migrateApiWorld(
         LegacyCraftBukkitWorldMigration.migrateApiWorld(new WorldMigrationContext(rootAccess, registryAccess, worldName, stemKey, dimensionKey));
     }
 
-    private static synchronized void warnAndDelayStartupMigration() throws IOException {
+    public static synchronized void warnAndDelayStartupMigration() {
         if (startupMigrationWarningShown) {
             return;
         }
@@ -77,7 +78,7 @@ private static synchronized void warnAndDelayStartupMigration() throws IOExcepti
                 Thread.sleep(30_000L);
             } catch (final InterruptedException ex) {
                 Thread.currentThread().interrupt();
-                throw new IOException("Interrupted while waiting before startup world migration", ex);
+                throw new RuntimeException("Interrupted while waiting before startup world migration", ex);
             }
         }
         LOGGER.info("Continuing with startup world migration.");

paper-server/src/main/java/io/papermc/paper/world/saveddata/PaperLevelOverrides.java

@@ -198,7 +198,7 @@ public boolean isDifficultyLocked() {
 
     private PrimaryLevelData rootDataOrThrow() {
         if (this.rootData == null) {
-            throw new IllegalStateException("PaperWorldLevelOverrides not attached");
+            throw new IllegalStateException(this.getClass().getName() + " not attached");
         }
         return this.rootData;
     }