fix(datastore): Update initial ChannelPool configs according to Datastore best practice guide #18190

Job	Run time
gitignore_correctness	1m 3s
gapic-bom	1m 47s
generate-readme	1m 6s
owlbot-py	1m 17s
root-pom	1m 40s
owlbot-yaml	1m 2s
package_name_check	1m 8s
group_id_check_for_maps_libraries	8m 1s
	17m 4s

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