Add tests for AttributedString Index Tracking preconditions #117

Job	Run time
Test / Linux (nightly-main - jammy)	10m 55s
Test / Windows (nightly-main - windows-2019)	19m 22s
Test / macOS (Xcode ${{ matrix.xcode_version }} - ${{ matrix.os_version }} - ${{ matrix.arch }})	0s
Soundness / API breakage check	0s
Soundness / Documentation check	0s
Soundness / Unacceptable language check	0s
Soundness / Broken symlinks check	3s
Soundness / License headers check	0s
Soundness / Format check	0s
Soundness / Python lint check	7s
Soundness / Shell check	31s
Soundness / YAML lint check	6s
	31m 4s

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