Define self variable so it can be used in instantiations #3233

Job	Run time
check-diff / check	20s
serialization / serialization-tests	9m 43s
c / ccpp / regular-tests (ubuntu-latest)	22m 43s
c / benchmarking / benchmark-tests	6m 38s
c / default / regular-tests (ubuntu-latest)	26m 20s
c / verifier / run (ubuntu-latest)	7m 58s
cpp / cpp-benchmark-tests / benchmark-tests	11m 47s
cpp / cpp-ros2-tests / cpp-ros2-tests	43m 52s
cpp / cpp-tests / regular-tests (ubuntu-latest)	50m 4s
py / py-tests / regular-tests (ubuntu-latest)	19m 33s
rs / rs-benchmark-tests / benchmark-tests	15m 26s
rs / rs-tests / regular-tests (ubuntu-latest, stable)	10m 41s
ts / benchmarking / benchmark-tests	5m 37s
ts / ts-tests / regular-tests (ubuntu-latest)	19m 24s
	4h 10m 6s

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