[sdk-platform-java] Native showcase CI tests don't run certain showcase tests

Certain showcase tests are being excluded from the native showcase CI tests. Example: EchoClientHttpJsonTest and ComplianceClientTest

If you look at this [CI showcase build](https://github.com/googleapis/sdk-platform-java/actions/runs/11355074289/job/31583690305) it includes these tests and it uses the command

```
mvn verify \
-P enable-integration-tests \
--batch-mode \
--no-transfer-progress

```

If you look at this [native CI build](https://github.com/googleapis/sdk-platform-java/actions/runs/11355074289/job/31583690528) it does not include these test. Command below:

```
mvn test -Pnative,-showcase -ntp -B
```