Bigtable: Move admin api into its own artifact. (#3494)
Bigtable: Move admin api into its own artifact. (#3494)

The target usecases are different enough that the clients should be split.
Also, it avoids confusion associated with duplicate static names.

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