Add C `Contracts` package #3301

Job	Run time
Prepare CodeQL unit test matrix	3s
Run unit tests (cpp, 2.18.4, codeql-cli/v2.18.4, codeql-bundle-v2.18.4, ubuntu-latest-xl, codeql-...	1h 35m 35s
Run unit tests (c, 2.18.4, codeql-cli/v2.18.4, codeql-bundle-v2.18.4, ubuntu-latest-xl, codeql-cl...	34m 8s
Validate test results	4s
	2h 9m 50s

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