Introduce DeprecatedGlobal and show proper warnings (#1014)

* kill the PyScript class and the weird pyscript instance; from the user point of view its functionalities are still available as pyscript.*, but pyscript is not the module, not the instance of PyScript

* simplify the code in _set_version_info, while I'm at it

* start to implement DeprecatedGlobal

* DeprecatedGlobal.__getattr__

* don't show the same warning twice

* DeprecatedGlobal.__call__

* make it possible to specify a different warning message for every global

* WIP: carefully use DeprecatedGlobal to show reasonable warning messages depending on which name you are accessing to. More names to follow

* deprecate more names

* deprecate private names

* depreacte direct usage of console and document

* deprecate the PyScript class

* use a better error message

* fix test_pyscript.py

* introduce a __repr__ for DeprecatedGlobal

* add an helper to ensure that we don't show any error or warning on the page

* WIP: ensure that examples don't use depreacted features. Many tests are failing

* don't deprecate Element

* don't use the global micropip to install packages, else we trigger a warning

* use a better error message for micropip

* fix test_todo_pylist to avoid using deprecated globals

* fix test_webgl_raycaster

* fix tests

* make HTML globally available

* add MIME_RENDERERS and MIME_METHODS

* fix the typing of Micropip, thanks to @FabioRosado

pyscriptjs/tests/integration/support.py

@@ -292,6 +292,17 @@ class PyScriptTest:
         elems = [loc.nth(i) for i in range(n)]
         return iter(elems)
 
+    def assert_no_banners(self):
+        """
+        Ensure that there are no alert banners on the page, which are used for
+        errors and warnings. Raise AssertionError if any if found.
+        """
+        loc = self.page.locator(".alert-banner")
+        n = loc.count()
+        if n > 0:
+            text = "\n".join(loc.all_inner_texts())
+            raise AssertionError(f"Found {n} alert banners:\n" + text)
+
 
 # ============== Helpers and utility functions ==============