Extract gcloud-maven-plugin, bigtable-emulator (#6452)
Extract gcloud-maven-plugin, bigtable-emulator (#6452)

* Extract gcloud-maven-plugin to https://github.com/googleapis/java-gcloud-maven-plugin

* extract bigtable emulator to https://github.com/googleapis/java-bigtable-emulator

googleapis/java-cloud-bom,googleapis/java-cloud-bom,googleapis/java-cloud-bom,googleapis/java-cloud-bom