Only expose selected objects in components module (#8873)

## Describe your changes

Usage of `*` in import is a bit problematic. I double-checked in Github,
and exposed the objects that seems to be relevant based on this
analysis.

## Testing Plan

- No logic changes.

---

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Author: lukasmasuch

lib/streamlit/components/v1/components.py

@@ -19,7 +19,20 @@
 # Since we do not know what other internals are used out in the wild, let's try to
 # model the old behavior and not to break things.
 
+# This should be cleaned up in the future, e.g. as part of components v2.
+
 from streamlit.components.v1.component_registry import (
-    declare_component as declare_component,  # noqa: PLC0414
+    declare_component,
+)
+from streamlit.components.v1.custom_component import (
+    CustomComponent,
+    MarshallComponentException,
 )
-from streamlit.components.v1.custom_component import *  # noqa: F403
+from streamlit.runtime.state import register_widget
+
+__all__ = [
+    "CustomComponent",
+    "declare_component",
+    "MarshallComponentException",
+    "register_widget",
+]