Add benchmark for saved state performance

- Introduced `benchmark_saved_state.gd` to evaluate the performance of the saved state restoration process.
- Implemented JSON integer restoration to handle large integers accurately.
- Added command-line argument parsing for specifying the path to the diagnostic JSON file and optional delta seconds.
- Conducted performance tests at different speeds and logged the elapsed time for six consecutive steps.
- Created a new UID file for the benchmark script.

tests/benchmark_saved_state.gd

@@ -0,0 +1,47 @@
+extends SceneTree
+## Read-only benchmark. Loads a diagnostic JSON, never invokes SaveManager.
+const E = preload("res://world/owniverse/math/exact.gd")
+
+func _initialize():
+    call_deferred("run")
+
+func restore_json_integers(value):
+    # JSON parses ordinary integer tokens as float. Large integers are $exact.
+    if value is float and value == floorf(value) and absf(value) <= 9007199254740991:
+        return int(value)
+    if value is Dictionary:
+        for key in value: value[key] = restore_json_integers(value[key])
+    elif value is Array:
+        for i in value.size(): value[i] = restore_json_integers(value[i])
+    return value
+
+func run():
+    var args = OS.get_cmdline_user_args()
+    if args.is_empty():
+        print("Usage: --script tests/benchmark_saved_state.gd -- /path/to/save.adventure.json [delta_seconds]")
+        quit(1)
+        return
+    var data = JSON.parse_string(FileAccess.get_file_as_string(args[0]))
+    if not data is Dictionary or data.get("format_version") != 3:
+        push_error("Expected diagnostic JSON format 3")
+        quit(1)
+        return
+    var initial: Dictionary = E.decode(restore_json_integers(data)).state
+    var delta: float = args[1].to_float() if args.size() > 1 else 1.0 / 60.0
+    if not is_finite(delta) or delta <= 0:
+        quit(1)
+        return
+    for speed in [1, 4, 6]:
+        var world = load("res://world/owniverse/owniverse.gd").new()
+        world.catalog.load_definitions(root.get_node("Global").OwniverseEntities)
+        world.state = initial.duplicate(true)
+        world.speed = speed
+        var elapsed: Array = []
+        for cycle in 6:
+            var start: int = Time.get_ticks_usec()
+            world.evolute(delta)
+            elapsed.append((Time.get_ticks_usec() - start) / 1000.0)
+        print("Speed %d, six consecutive %s-second steps, ms: %s" % [speed, delta, elapsed])
+        for entity in world.catalog.entities.values(): entity.free()
+        world.free()
+    quit()