[Diagnostic formatting] Add a category footnote printer #52

Job	Run time
Run tests using swift-syntax-dev-utils (Windows)	40m 14s
Validate generated code	3m 1s
Run tests using swift-syntax-dev-utils (Linux)	24m 33s
Test / Linux (5.8 - jammy)	3m 42s
Test / Windows (5.9 - windows-2022)	14m 16s
Test / Linux (5.9 - jammy)	3m 53s
Test / Windows (6.0 - windows-2022)	12m 20s
Test / Windows (nightly - windows-2019)	15m 3s
Test / Linux (5.10 - jammy)	3m 51s
Test / Windows (nightly-6.1 - windows-2019)	15m 13s
Test / Linux (6.0 - jammy)	3m 54s
Test / Linux (nightly-main - jammy)	4m 42s
Test / Linux (nightly-6.1 - jammy)	4m 40s
Soundness / API breakage check	3m 4s
Soundness / Broken symlinks check	5s
Soundness / Documentation check	4m 58s
Soundness / License headers check	9s
Soundness / Format check	36s
Soundness / Python lint check	7s
Soundness / Shell check	30s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	5s
	2h 38m 59s

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