Add workflow permissions #3942

Job	Run time
Prepare CodeQL unit test matrix	6s
Run unit tests (cpp, 2.20.7, codeql-cli/v2.20.7, codeql-bundle-v2.20.7, ubuntu-latest-xl, codeql-...	1h 43m 57s
Run unit tests (c, 2.20.7, codeql-cli/v2.20.7, codeql-bundle-v2.20.7, ubuntu-latest-xl, codeql-cl...	36m 3s
Validate test results	7s
	2h 20m 13s

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