Run one testsuite with observers enabled in CI (#13869)

Signed-off-by: Bob Weinand <bobwei9@hotmail.com>

Fix GH-12905: FFI::new interacts badly with observers

Because these functions are copied and not properly registered (which we
can't), the observer code doesn't add the temporaries on st

Fix GH-12905: FFI::new interacts badly with observers

Because these functions are copied and not properly registered (which we
can't), the observer code doesn't add the temporaries on startup.
Add them via a callback during startup.

Closes GH-12906.

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