Add type-safe `VecMap` for slices indexed by newtypes #458

Job	Run time
Configure	4s
Integration Neko	6m 52s
Lint / Lint	5m 0s
Unit Rust / ubuntu-latest	8m 12s
Documentation / Docs	12m 18s
Miri / Miri	8m 47s
QPY / Test	9m 5s
Image / Test-images-3.10	3m 46s
Unit Python / Windows / Python oldest / windows-latest - Python 3.10	25m 40s
Unit Python / Windows / Python newest / windows-latest - Python 3.14	23m 34s
Unit Python / macOS / Python oldest / macos-15 - Python 3.10	14m 56s
Unit Python / macOS / Python newest / macos-15 - Python 3.14	9m 7s
Unit Python / Linux / Python oldest - ubuntu-24.04-arm / ubuntu-24.04-arm - Python 3.10	13m 35s
Unit Python / Linux / Python oldest - ubuntu-latest / ubuntu-latest - Python 3.10	19m 18s
Unit Python / Linux / Python newest - ubuntu-24.04-arm / ubuntu-24.04-arm - Python 3.14	8m 41s
Unit C / ubuntu-24.04-arm / ubuntu-24.04-arm	3m 17s
Unit C / macos-15 / macos-15	2m 26s
Unit C / ubuntu-latest / ubuntu-latest	2m 45s
Unit C / windows-latest / windows-latest	4m 34s
Unit Python / Linux / Python newest - ubuntu-latest / ubuntu-latest - Python 3.14	10m 53s
Finalize	3s
	3h 12m 53s

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