[Inference] ADD async and sync Api server using FastAPI (#5396)

* add api server

* fix

* add

* add completion service and fix bug

* add generation config

* revise shardformer

* fix bugs

* add docstrings and fix some bugs

* fix bugs and add choices for prompt template

colossalai/inference/server/utils.py

@@ -0,0 +1,16 @@
+# make it singleton
+class NumericIDGenerator:
+    _instance = None
+
+    def __new__(cls):
+        if cls._instance is None:
+            cls._instance = super(NumericIDGenerator, cls).__new__(cls)
+            cls._instance.current_id = 0
+        return cls._instance
+
+    def __call__(self):
+        self.current_id += 1
+        return self.current_id
+
+
+id_generator = NumericIDGenerator()