Set dev.system test_dir and remove docker label for dev.system

[sophia-guo]

Fix adoptium/temurin-build#3674

also remove docker requirement for dev.system as this is not required for reproducible comparing tests.

Current test_dirs(VENDOR_DIRS) supports multi dirs separated by comma. However that is multi dir strings for multi Vendor_repos. That is one test_dir for one vendor_repo. So we can't do this by set default test_dirs to "/test/functional, /test/system" in defaults.jason.

[github-actions]

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[sophia-guo]

Testing build https://ci.adoptium.net/view/Test_system/job/Test_openjdk21_hs_dev.system_x86-64_linux/19/console