feat: use default config path when no arg for -f is provided #14016

Job	Run time
check_if_release_branch	1s
changed_files	5s
towncrier_check	7s
build mirrord CLI	0s
test_agent_image	24s
lint	3m 31s
check-rust-docs	59s
integration_tests	12m 16s
macos_tests	25m 28s
test_agent	3m 28s
test_cli_image	15m 26s
lint_markdown	0s
vscode_e2e_on_release_branch	0s
e2e (docker)	16m 14s
intellij_e2e_on_release_branch	0s
e2e (containerd)	14m 59s
ci	1s
	1h 32m 59s

Provide feedback