Setup `contrib/` directory with CODEOWNERS that is extensible for non-SDK team extensions. #2540

Job	Run time
Code format	56s
Unit test with cloud	4m 39s
Unit test with docker service [JDK8]	14m 7s
Javadoc	3m 12s
Build native test server / Build native test server (ubuntu-24.04-arm, linux, arm64)	6m 46s
Unit test with in-memory test service [Edge]	11m 30s
Build native test server / Build native test server (macos-15-intel, macOS, amd64)	14m 24s
Build native test server / Build native test server (ubuntu-latest, linux, amd64, true)	6m 28s
Build native test server / Build native test server (windows-latest, windows, amd64)	6m 19s
Build native test server / Build native test server (macos-latest, macOS, arm64)	6m 30s
Build native test server / Build native test server (ubuntu-latest, linux, amd64, false)	6m 53s
	1h 21m 44s

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