Add additional options to PR template and clarify some #6355

Job	Run time
Ruby analysis (ubuntu-latest, default)	49s
Ruby analysis (macos-latest, linked)	1m 42s
Ruby analysis (macos-latest, default)	1m 28s
Ruby analysis (ubuntu-latest, nightly-latest)	50s
Ruby analysis (macos-latest, nightly-latest)	1m 3s
Ruby analysis (ubuntu-latest, linked)	49s
	6m 41s

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