⚡ improve plugin system (#1011)

tests/test_plugin/test_manager.py

@@ -0,0 +1,12 @@
+import pytest
+from nonebug import App
+
+
+@pytest.mark.asyncio
+async def test_load_plugin_name(app: App):
+    from nonebot.plugin import PluginManager
+
+    m = PluginManager(plugins=["plugins.export"])
+    module1 = m.load_plugin("export")
+    module2 = m.load_plugin("plugins.export")
+    assert module1 is module2