fuzz: more initialized memory for MSAN #2403

Job	Run time
build on macos (macos-latest)	1m 13s
build on fedora:40 (gcc, true)	1m 45s
build on macos (macos-latest-xlarge)	48s
build on ubuntu:24.04 (gcc,false)	1m 24s
build on fedora:40 (clang, false)	1m 36s
build on ubuntu:24.04 (clang,false)	1m 27s
build on fedora:39 (gcc, false)	1m 55s
build on ubuntu:23.10 (gcc,false)	1m 11s
build on fedora:39 (clang, false)	1m 45s
build on ubuntu:23.10 (clang,false)	1m 32s
build on ubuntu:22.04 (gcc,false)	1m 13s
build on ubuntu:22.04 (clang,true)	1m 26s
build on ubuntu:20.04 (gcc,false)	1m 23s
build on ubuntu:20.04 (clang,false)	1m 33s
build on debian:12 (gcc,false)	1m 22s
build on debian:12 (clang,false)	1m 36s
build on debian:11 (gcc,false)	1m 20s
build on debian:11 (clang,false)	1m 34s
run unit tests (ubuntu:22.04, clang)	12m 10s
run unit tests (fedora:40, gcc)	11m 51s
	50m 4s

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