Add builtin `List.walkWithIndexUntil` #236

Job	Run time
check-changes	17s
ran-none	0s
start-nix-linux-aarch64-build-default-test / nix-linux-arm64	36m 10s
start-macos-x86-64-tests / test-rust-macos-x86-64	18m 11s
start-nix-linux-aarch64-cargo-build-test / nix-linux-arm64	1h 6m 16s
start-nix-macos-apple-silicon-tests / nix-apple-silicon	3m 4s
start-nix-linux-x86-64-tests / nix-linux-x86	37m 51s
start-roc-benchmarks / benchmark roc programs	5m 57s
start-ubuntu-x86-64-tests / test zig, rust, wasm...	13m 59s
start-windows-release-build-test / windows-release-build	13m 23s
start-windows-tests / windows-test-subset	25m 17s
ran-full	0s
finish	1s
	3h 40m 26s

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