Generalize categoryFootnotes to work on any sequence #55

Job	Run time
Run tests using swift-syntax-dev-utils (Linux)	24m 28s
Validate generated code	3m 2s
Run tests using swift-syntax-dev-utils (Windows)	40m 18s
Test / Linux (5.8 - jammy)	3m 41s
Test / Windows (5.9 - windows-2022)	23m 11s
Test / Linux (5.9 - jammy)	3m 53s
Test / Windows (6.0 - windows-2022)	19m 26s
Test / Linux (5.10 - jammy)	3m 50s
Test / Windows (nightly - windows-2019)	16m 33s
Test / Linux (6.0 - jammy)	3m 58s
Test / Windows (nightly-6.1 - windows-2019)	14m 46s
Test / Linux (nightly-main - jammy)	4m 39s
Test / Linux (nightly-6.1 - jammy)	4m 56s
Soundness / API breakage check	3m 11s
Soundness / Documentation check	4m 17s
Soundness / License headers check	9s
Soundness / Unacceptable language check	5s
Soundness / Broken symlinks check	4s
Soundness / Format check	44s
Soundness / Python lint check	6s
Soundness / Shell check	31s
Soundness / YAML lint check	3s
	2h 55m 51s

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