feat: use default config path when no arg for -f is provided #14027

Job	Run time
check_if_release_branch	1s
towncrier_check	8s
changed_files	6s
build mirrord CLI	0s
test_agent_image	6m 53s
check-rust-docs	1m 6s
lint	3m 32s
test_agent	3m 34s
test_cli_image	6m 44s
integration_tests	12m 45s
lint_markdown	0s
macos_tests	19m 23s
e2e (docker)	14m 41s
intellij_e2e_on_release_branch	0s
e2e (containerd)	13m 17s
vscode_e2e_on_release_branch	0s
ci	1s
	1h 22m 11s

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