Isolated chunk update failures

- Treats only loading saved biome information as an engine failure
- Leaves a container without loot and warns once when its saved biome cannot be recovered
- Keeps a failed chunk unetched and retries it without stopping the rest of the level's update pass
- Ends a level's pass only when its engine or mantle is closed
- Covers the deferred, permanent and isolated update paths through updateChunk and the server tick

core/src/main/java/art/arcane/iris/generation/runtime/GenerationFailures.java

@@ -31,7 +31,7 @@ public final class GenerationFailures {
                     || current instanceof GenerationClosedException
                     || current instanceof MantleClosedException
                     || current instanceof WrongEngineBroException
-                    || current instanceof SavedBiomeUnavailableException
+                    || current instanceof SavedBiomeUnavailableException unavailable && unavailable.isLoading()
                     || current instanceof InterruptedException
                     || current instanceof InterruptedIOException
                     || current instanceof ClosedChannelException