Support both aggregation response shapes for metric tag configurations #19016

Job	Run time
test / test (2.7, ubuntu-latest)	4m 27s
test / test (3.2, ubuntu-latest)	3m 33s
test / test (jruby-9.4.12.0, ubuntu-latest)	4m 6s
examples / examples	2m 37s
pre-commit / pre-commit	1m 30s
report	11s
	16m 24s

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