test: unify assertSnapshot common patterns #2849

Job	Run time
Build slim tarball	1m 47s
x86_64-linux: with shared libraries	1h 58m 44s
aarch64-darwin: with shared libraries	1h 58m 53s
aarch64-linux: with shared libraries	1h 25m 24s
x86_64-darwin: with shared libraries	59m 37s
	6h 24m 25s

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