feat(gax): Add error attributes to golden signal metrics. #18586

Job	Run time
changes	5s
enforcer	1m 53s
gapic-libraries-bom	1m 54s
lint	3m 31s
generation-config-check	1m 40s
units (8)	2m 2s
windows	2m 8s
units (21)	1m 34s
units (25)	1m 40s
units (11)	1m 34s
units (17)	1m 45s
split-units (sdk-platform-java, 17)	2m 27s
split-units (sdk-platform-java, 21)	1m 45s
split-units (sdk-platform-java, 25)	2m 12s
split-units (sdk-platform-java, 8)	2m 0s
split-units (sdk-platform-java, 11)	1m 50s
	30m 0s

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