Re-export Event in types.py (#2829)

End-users may need to use the Event type for their type hinting to work following the Event type changes. However, we define Event in a private module sentry_sdk._types, which provides no stability guarantees.

Therefore, this PR creates a new public module sentry_sdk.types, where we re-export the Event type, and explicitly make it available as public API via sentry_sdk.types.Event. The new sentry_sdk.types module includes a docstring to inform users that we reserve the right to modify types in minor releases, since we consider types to be a form of documentation (they are not enforced by the Python language), but that we guarantee that we will only remove type definitions in a major release.

sentry_sdk/types.py

@@ -0,0 +1,14 @@
+"""
+This module contains type definitions for the Sentry SDK's public API.
+The types are re-exported from the internal module `sentry_sdk._types`.
+
+Disclaimer: Since types are a form of documentation, type definitions
+may change in minor releases. Removing a type would be considered a
+breaking change, and so we will only remove type definitions in major
+releases.
+"""
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from sentry_sdk._types import Event, Hint  # noqa: F401