doc: Add metrics documentation and add a 'Reference' section #362

Job	Run time
build (cuda) / build-and-push	9m 42s
build (intel) / build-and-push	11m 19s
build (rocm) / build-and-push	14m 37s
build (cuda) / integration_tests	8m 9s
build (intel) / integration_tests	0s
build (rocm) / integration_tests	0s
	43m 47s

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