feat(datastore): Enable Otel metrics for custom Otel #20066

Job	Run time
bulk-filter	1m 5s
changes	3s
windows	2m 13s
enforcer	14m 44s
generation-config-check	1m 45s
lint	4m 28s
gapic-libraries-bom	18m 52s
split-dependencies (java-datastore)	4m 5s
split-units (java-datastore, 8)	2m 53s
split-clirr (java-datastore)	2m 58s
split-units (java-datastore, 21)	4m 24s
split-units (java-datastore, 25)	4m 47s
split-units (java-datastore, 17)	4m 44s
split-units (java-datastore, 11)	3m 31s
units (8)	44s
units (11)	30s
units (25)	32s
units (17)	34s
units (21)	30s
conditional-required-check	3s
	1h 13m 25s

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