Use `target.namespace` for targetless runs #14101

Job	Run time
check_if_release_branch	1s
towncrier_check	7s
changed_files	6s
build mirrord CLI	0s
check-rust-docs	3m 35s
lint	11m 6s
test_agent_image	19s
test_agent	3m 19s
integration_tests	11m 22s
macos_tests	18m 46s
lint_markdown	0s
test_cli_image	15m 31s
vscode_e2e_on_release_branch	0s
e2e (docker)	8m 4s
intellij_e2e_on_release_branch	0s
e2e (containerd)	10m 9s
ci	1s
	1h 22m 26s

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