Utility function/decorator to mark things as Sentry-patched

While reviewing #3358, I had the idea that we might want to make it easier to detect when the SDK has already patched something. This came up because with the `@ensure_integration_enabled` decorator, the function's `__name__` (and similar attributes) are overwritten to make the function look like the original function, so we cannot use these attributes to detect that a function has been patched by Sentry. I originally thought adding this would be necessary for that PR to work, but turns out we don't need it, so I am documenting this idea here, instead.

We could add this to the `@ensure_integration_enabled` decorator and/or make a separate decorator. The decorator would set an attribute called something like `_sentry_patched` on the patched function/class/etc. We could set this attribute simply to `True`, or if we want to make it more informative, maybe we can include some information about what patched the function (maybe the integration class/identifier – we can think about what would be the most helpful).