Add a /free route to unload models or free all memory.

A POST request to /free with: {"unload_models":true}
will unload models from vram.

A POST request to /free with: {"free_memory":true}
will unload models and free all cached data from the last run workflow.

execution.py

@@ -268,11 +268,14 @@ def recursive_output_delete_if_changed(prompt, old_prompt, outputs, current_item
 
 class PromptExecutor:
     def __init__(self, server):
+        self.server = server
+        self.reset()
+
+    def reset(self):
         self.outputs = {}
         self.object_storage = {}
         self.outputs_ui = {}
         self.old_prompt = {}
-        self.server = server
 
     def handle_execution_error(self, prompt_id, prompt, current_outputs, executed, error, ex):
         node_id = error["node_id"]
@@ -706,6 +709,7 @@ class PromptQueue:
         self.queue = []
         self.currently_running = {}
         self.history = {}
+        self.flags = {}
         server.prompt_queue = self
 
     def put(self, item):
@@ -792,3 +796,17 @@ class PromptQueue:
     def delete_history_item(self, id_to_delete):
         with self.mutex:
             self.history.pop(id_to_delete, None)
+
+    def set_flag(self, name, data):
+        with self.mutex:
+            self.flags[name] = data
+            self.not_empty.notify()
+
+    def get_flags(self, reset=True):
+        with self.mutex:
+            if reset:
+                ret = self.flags
+                self.flags = {}
+                return ret
+            else:
+                return self.flags.copy()