Add `proxy_ca_certificate_file` output to `start-proxy` action #4694

Job	Run time
Ruby analysis (macos-latest, linked)	57s
Ruby analysis (ubuntu-latest, nightly-latest)	45s
Ruby analysis (ubuntu-latest, linked)	47s
Ruby analysis (macos-latest, default)	54s
Ruby analysis (macos-latest, nightly-latest)	50s
Ruby analysis (ubuntu-latest, default)	46s
	4m 59s

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