Allow parsing of "nonisolated" as a type specifier along with "isolated" #68

Job	Run time
Validate generated code	2m 58s
Run tests using swift-syntax-dev-utils (Linux)	3m 10s
Run tests using swift-syntax-dev-utils (Windows)	26m 9s
Test / Windows (5.9 - windows-2022)	29m 19s
Test / Linux (5.8 - jammy)	3m 46s
Test / Windows (6.0 - windows-2022)	22m 13s
Test / Linux (5.9 - jammy)	3m 52s
Test / Windows (nightly - windows-2019)	15m 48s
Test / Linux (5.10 - jammy)	3m 51s
Test / Windows (nightly-6.1 - windows-2019)	16m 58s
Test / Linux (6.0 - jammy)	4m 2s
Test / Linux (nightly-main - jammy)	5m 5s
Test / Linux (nightly-6.1 - jammy)	4m 37s
Soundness / API breakage check	0s
Soundness / Documentation check	5m 6s
Soundness / Unacceptable language check	4s
Soundness / Broken symlinks check	3s
Soundness / License headers check	11s
Soundness / Format check	36s
Soundness / Shell check	33s
Soundness / Python lint check	6s
Soundness / YAML lint check	3s
	2h 28m 30s

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