feat(gax): Add error attributes to golden signal metrics. #18585

Job	Run time
changes	4s
units (25)	1m 38s
enforcer	1m 52s
units (21)	1m 36s
units (11)	1m 41s
generation-config-check	1m 40s
gapic-libraries-bom	1m 50s
windows	2m 25s
lint	3m 10s
units (8)	1m 58s
units (17)	1m 37s
split-units (sdk-platform-java, 11)	4m 35s
split-units (sdk-platform-java, 17)	2m 32s
split-units (sdk-platform-java, 21)	1m 52s
split-units (sdk-platform-java, 8)	1m 58s
split-units (sdk-platform-java, 25)	1m 43s
	32m 11s

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