feat(gax): Add error attributes to golden signal metrics. #17211

Job	Run time
gapic-bom	1m 39s
owlbot-py	1m 8s
gitignore_correctness	1m 0s
owlbot-yaml	1m 0s
root-pom	1m 43s
group_id_check_for_maps_libraries	7m 45s
generate-readme	1m 6s
package_name_check	1m 1s
	16m 22s

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