Refactor more types and fix ruff check warnings

Lots of Dict -> dict; List -> list and some other cleanups here and
there.

one of the rules is apparently python style standards say it's illegal
to name a variable 'l' (or i or o), so may as well fix it just so the
warning goes away too.

ib_async/__init__.py

@@ -135,6 +135,8 @@
     "FlexError",
     "FlexReport",
     "IB",
+    "IBDefaults",
+    "OrderStateNumeric",
     "IBC",
     "Watchdog",
     "AccountValue",

ib_async/client.py

@@ -296,7 +296,7 @@ def send(self, *fields, makeEmpty=True):
             bool: lambda b: "1" if b else "0",
 
             # Lists of tags become semicolon-appended KV pairs
-            list: lambda l: "".join([f"{v.tag}={v.value};" for v in l]),
+            list: lambda lst: "".join([f"{v.tag}={v.value};" for v in lst]),
         }
         # fmt: on
 

ib_async/decoder.py

@@ -2,7 +2,7 @@
 
 import dataclasses
 import logging
-from datetime import datetime, timezone
+from datetime import datetime
 from typing import Any, cast
 
 from .contract import (