index: organize Index and IndexStore errors into enums #6816

Job	Run time
check (protos)	2m 32s
check (doctests)	2m 58s
check (cargo-deny, bans)	23s
check (mkdocs)	16s
check (cargo-deny, advisories)	26s
check (cargo-deny, licenses)	31s
check (cargo-deny, sources)	30s
check (clippy)	1m 40s
nix flake (ubuntu-24.04)	7m 44s
check (zizmor)	35s
check (rustfmt)	21s
check (codespell)	10s
check (latest mkdocs, optional)	7m 17s
nix flake (ubuntu-24.04-arm)	7m 21s
build (no git)	1m 31s
check (Cargo.lock dependency count)	6s
test (linux-aarch64-gnu)	6m 25s
test (macos-x86_64)	5m 17s
test (macos-aarch64)	9m 3s
test (windows-aarch64)	15m 8s
test (windows-x86_64)	21m 16s
nix flake (macos-14)	13m 18s
test (linux-x86_64-gnu)	6m 20s
required checks (merge queue)	0s
	1h 51m 8s

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