Add policy to exclude env vars. #13611

Job	Run time
towncrier_check	6s
check_if_release_branch	1s
changed_files	6s
build mirrord CLI	0s
check-rust-docs	1m 54s
lint	10m 27s
integration_tests	6m 34s
lint_markdown	0s
macos_tests	19m 1s
test_agent	3m 9s
test_agent_image	18s
test_cli_image	5m 58s
vscode_e2e_on_release_branch	0s
e2e (docker)	14m 17s
intellij_e2e_on_release_branch	0s
e2e (containerd)	11m 50s
ci	1s
	1h 13m 42s

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