Setup `contrib/` directory with CODEOWNERS that is extensible for non-SDK team extensions. #2545

Job	Run time
Unit test with docker service [JDK8]	13m 39s
Unit test with cloud	4m 47s
Code format	46s
Unit test with in-memory test service [Edge]	11m 21s
Javadoc	3m 12s
Build native test server / Build native test server (ubuntu-latest, linux, amd64, true)	6m 10s
Build native test server / Build native test server (macos-latest, macOS, arm64)	11m 38s
Build native test server / Build native test server (windows-latest, windows, amd64)	6m 19s
Build native test server / Build native test server (ubuntu-24.04-arm, linux, arm64)	6m 58s
Build native test server / Build native test server (ubuntu-latest, linux, amd64, false)	7m 1s
Build native test server / Build native test server (macos-15-intel, macOS, amd64)	17m 5s
	1h 28m 56s

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