Add exemplar support to the prometheus exporter #11320

Job	Run time
lint	2m 0s
compatibility-test (~1.22.0, ubuntu-latest, 386)	1m 6s
compatibility-test (~1.22.0, ubuntu-latest, amd64)	28s
test-bench	39s
compatibility-test (~1.22.0, macos-latest, amd64)	1m 22s
compatibility-test (~1.22.0, windows-latest, 386)	2m 43s
test-coverage	51s
compatibility-test (~1.22.0, windows-latest, amd64)	3m 11s
compatibility-test (~1.22.0, actuated-arm64-2cpu-8gb, arm64)	1m 40s
compatibility-test (~1.21.3, ubuntu-latest, 386)	21s
test-race	1m 56s
compatibility-test (~1.21.3, ubuntu-latest, amd64)	59s
compatibility-test (~1.21.3, macos-latest, amd64)	1m 15s
compatibility-test (~1.21.3, windows-latest, 386)	7m 16s
compatibility-test (~1.21.3, windows-latest, amd64)	3m 16s
compatibility-test (~1.21.3, actuated-arm64-2cpu-8gb, arm64)	1m 39s
test-compatibility	1s
	30m 43s

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