Store insertion order using offsets #3090

Job	Run time
aarch64-apple-darwin/clang	11m 6s
x86_64-unknown-linux-gnu/gcc	10m 6s
aarch64-unknown-linux-gnu/gcc	7m 13s
x86_64-unknown-linux-gnu/gcc-free-threading	8m 14s
x86_64-apple-darwin/clang	17m 59s
	54m 38s

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