Bump upb version and refactor python compatibility.

This pulls in updates to system_python, which allows for better handling of our non-hermetic setup.  Specifically, our python tests are marked incompatible on systems without a python installation.  This will cause them to get skipped by wildcard expansions (which is why we add 1 explicit target to the kokoro builds).

PiperOrigin-RevId: 492286518
diff --git a/python/internal.bzl b/python/internal.bzl
index e9bcb27..d9ba37e 100644
--- a/python/internal.bzl
+++ b/python/internal.bzl
@@ -106,3 +106,20 @@
         }),
         **kwargs
     )
+
+def internal_py_test(deps = [], **kwargs):
+    """Internal wrapper for shared test configuration
+
+    Args:
+      deps: any additional dependencies of the test.
+      **kwargs: arguments forwarded to py_test.
+    """
+    native.py_test(
+        imports = ["."],
+        deps = deps + [":python_test_lib"],
+        target_compatible_with = select({
+            "@system_python//:supported": [],
+            "//conditions:default": ["@platforms//:incompatible"],
+        }),
+        **kwargs
+    )