Make google_oracle_database_autonomous_database.name field unique per acceptance test

[modular-magician]

Latest PR in my effort to close the ticket about failing Oracle resource tests. This PR is to address this issue that impacts:

• TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseFullExample
• TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseBasicExample

------- Stdout: -------
=== RUN   TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseFullExample
=== PAUSE TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseFullExample
=== CONT  TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseFullExample
    resource_oracle_database_autonomous_database_generated_test.go:96: Step 1/2 error: Error running apply: exit status 1
        Error: Error waiting to create AutonomousDatabase: Error waiting for Creating AutonomousDatabase: Error code 3, message: generic::invalid_argument: InvalidParameter: Provisioning Autonomous Database failed Cause: Provisioning failed because a database named testdatabase already exists in compartment 466158962507. The name must be unique among all Autonomous Data Warehouses and Autonomous Databases in your tenancy in the same region. Specify a different database name and try again.
          with google_oracle_database_autonomous_database.myADB,
          on terraform_plugin_test.tf line 2, in resource "google_oracle_database_autonomous_database" "myADB":
           2: resource "google_oracle_database_autonomous_database" "myADB"{
--- FAIL: TestAccOracleDatabaseAutonomousDatabase_oracledatabaseAutonomousDatabaseFullExample (503.35s)
FAIL

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Derived from GoogleCloudPlatform/magic-modules#12511