feat(gax): Add error attributes to golden signal metrics. #595

Job	Run time
filter	1m 15s
build(8) for gapic-generator-java	11m 11s
build(8) except for gapic-generator-java	3m 56s
unmanaged_dependency_check	7m 13s
build (17)	13m 2s
showcase (25)	8m 50s
build(25) except self-service clients	12m 37s
showcase-clirr	5m 19s
build (11)	13m 40s
dependency_analyzer_unit_test	1m 24s
build(8) for showcase	4m 55s
gapic-generator-java-bom	2m 5s
showcase (11)	8m 50s
build(21) except self-service clients	11m 46s
showcase (21)	8m 35s
showcase (17)	8m 53s
	2h 3m 31s

Provide feedback