Add C `Contracts` package #3315

Job	Run time
Prepare CodeQL unit test matrix	4s
Run unit tests (cpp, 2.18.4, codeql-cli/v2.18.4, codeql-bundle-v2.18.4, ubuntu-latest-xl, codeql-...	1h 31m 42s
Run unit tests (c, 2.18.4, codeql-cli/v2.18.4, codeql-bundle-v2.18.4, ubuntu-latest-xl, codeql-cl...	32m 12s
Validate test results	4s
	2h 4m 2s

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