Add C `Contracts` package #3300

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-...	22m 28s
Run unit tests (c, 2.18.4, codeql-cli/v2.18.4, codeql-bundle-v2.18.4, ubuntu-latest-xl, codeql-cl...	17m 9s
Validate test results	2s
	39m 42s

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