chore: move bigquery jdbc external test to monorepo #17185

Job	Run time
owlbot-py	1m 13s
gitignore_correctness	1m 0s
generate-readme	1m 12s
owlbot-yaml	1m 8s
root-pom	1m 40s
package_name_check	1m 8s
group_id_check_for_maps_libraries	8m 13s
gapic-bom	1m 46s
	17m 20s

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