Core, WebHost: lazy-load worlds in unpickler, WebHost and WebHostLib (#2156)

* Core: lazy-load worlds in unpickler

this should hopefully fix customserver's memory consumption

* WebHost: move imports around to save memory in MP

* MultiServer: prefer loading _speedups without pyximport

This saves ~15MB per MP and speeds up module import if it was built in-place.

* Tests: fix tests for changed WebHost imports

* CustomServer: run GC after setup

* CustomServer: cleanup exception handling

test/webhost/TestAPIGenerate.py

@@ -5,7 +5,8 @@ import json
 class TestDocs(unittest.TestCase):
     @classmethod
     def setUpClass(cls) -> None:
-        from WebHost import get_app, raw_app
+        from WebHostLib import app as raw_app
+        from WebHost import get_app
         raw_app.config["PONY"] = {
             "provider": "sqlite",
             "filename": ":memory:",

test/webhost/TestFileGeneration.py

@@ -14,7 +14,8 @@ class TestFileGeneration(unittest.TestCase):
         cls.incorrect_path = os.path.join(os.path.split(os.path.dirname(__file__))[0], "WebHostLib")
 
     def testOptions(self):
-        WebHost.create_options_files()
+        from WebHostLib.options import create as create_options_files
+        create_options_files()
         target = os.path.join(self.correct_path, "static", "generated", "configs")
         self.assertTrue(os.path.exists(target))
         self.assertFalse(os.path.exists(os.path.join(self.incorrect_path, "static", "generated", "configs")))