Update map iterator to be index based #3228

Job	Run time
cargo-deny (advisories)	3m 6s
cargo-deny (bans licenses sources)	2m 53s
build-fuzz	2m 3s
docs	5m 35s
build-and-test (ubuntu-latest, x86_64-unknown-linux-gnu)	9m 39s
build-and-test (macos-latest, x86_64-apple-darwin)	18m 29s
build-and-test (macos-latest, aarch64-apple-darwin)	17m 50s
build-and-test (windows-latest, x86_64-pc-windows-msvc)	16m 13s
fmt	10s
publish-dry-run	0s
rust-analyzer-compat	10m 41s
complete	1s
	1h 26m 40s

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