Use `target.namespace` for targetless runs #14100

Job	Run time
changed_files	7s
check_if_release_branch	1s
towncrier_check	7s
build mirrord CLI	0s
integration_tests	12m 51s
lint	11m 36s
check-rust-docs	3m 31s
lint_markdown	0s
macos_tests	16m 20s
test_agent	3m 29s
test_agent_image	6m 40s
test_cli_image	14m 55s
vscode_e2e_on_release_branch	0s
e2e (docker)	8m 27s
intellij_e2e_on_release_branch	0s
e2e (containerd)	8m 44s
ci	1s
	1h 26m 49s

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