chore: move bigquery jdbc external test to monorepo #17238

Job	Run time
gitignore_correctness	1m 16s
root-pom	1m 53s
group_id_check_for_maps_libraries	8m 10s
owlbot-yaml	1m 15s
owlbot-py	1m 9s
package_name_check	1m 8s
generate-readme	1m 23s
gapic-bom	1m 48s
	18m 2s

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