ZJIT: Use opt-level=0 in tests like before #12845

Job	Run time
make (check, --disable-yjit)	7m 7s
make (test-bundled-gems)	13m 2s
ruby-bench (--warmup=1 --bench=1 --excludes=shipit)	13m 58s
make (check, ubuntu-24.04, capi)	9m 50s
make-ibm	0s
make (test-bundler-parallel, 50)	21m 35s
make (check, --enable-shared --enable-load-relative)	8m 7s
make (check, cppflags=-DVM_CHECK_MODE)	8m 45s
make (check, i686)	11m 50s
Ubuntu result	3s
	1h 34m 17s

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