Add workflow permissions #3930

Job	Run time
Prepare CodeQL unit test matrix	12s
Run unit tests (cpp, 2.20.7, codeql-cli/v2.20.7, codeql-bundle-v2.20.7, ubuntu-latest-xl, codeql-...	1h 38m 33s
Run unit tests (c, 2.20.7, codeql-cli/v2.20.7, codeql-bundle-v2.20.7, ubuntu-latest-xl, codeql-cl...	34m 38s
Validate test results	5s
	2h 13m 28s

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