[tune] logger refactor part 1: move classes and utilities to own files (#11746)

* [tune] logger refactor part 1: move classes and utilities to own files

* Fix circular dependency

* Remove uneeded pretty print copy

* Apply suggestions from code review

python/ray/tune/utils/util.py

@@ -1,5 +1,7 @@
 import copy
+import json
 import logging
+import numbers
 import os
 import inspect
 import threading
@@ -538,6 +540,31 @@ def detect_config_single(func):
     return use_config_single
 
 
+class SafeFallbackEncoder(json.JSONEncoder):
+    def __init__(self, nan_str="null", **kwargs):
+        super(SafeFallbackEncoder, self).__init__(**kwargs)
+        self.nan_str = nan_str
+
+    def default(self, value):
+        try:
+            if np.isnan(value):
+                return self.nan_str
+
+            if (type(value).__module__ == np.__name__
+                    and isinstance(value, np.ndarray)):
+                return value.tolist()
+
+            if issubclass(type(value), numbers.Integral):
+                return int(value)
+            if issubclass(type(value), numbers.Number):
+                return float(value)
+
+            return super(SafeFallbackEncoder, self).default(value)
+
+        except Exception:
+            return str(value)  # give up, just stringify it (ok for logs)
+
+
 if __name__ == "__main__":
     ray.init()
     X = pin_in_object_store("hello")