HDDS-16247. Separate StorageContainerLocationProtocol RPC identity from its internal Java interface

[echonesis]

What changes were proposed in this pull request?

StorageContainerLocationProtocol currently serves two different purposes:

1. Its fully qualified class name is used as the historical Hadoop RPC protocol identity.
2. Its methods define the internal Java interface used by SCM clients and implementations.

The actual Hadoop RPC protocol is StorageContainerLocationProtocolPB, which extends the generated Protobuf blocking interface and provides the RPC protocol name, version, and Kerberos metadata. Keeping the internal Java methods in StorageContainerLocationProtocol incorrectly makes changes to an internal interface appear to be changes to the RPC protocol.

This pull request separates these responsibilities:

• Keeps StorageContainerLocationProtocol as an empty final class so that its historical FQCN remains available as the RPC identity.
• Moves the internal Java methods and constants to the new StorageContainerLocationInternalInterface.
• Updates internal implementations, clients, translators, SCM HA proxy handling, and callers to use the new internal interface.
• Adds focused tests confirming that:
  • StorageContainerLocationProtocolPB continues to provide the historical protocol name, version, and Kerberos metadata.
  • The RPC identity class is separate from the internal Java interface.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-16247

How was this patch tested?

Local Tests

mvn -pl :hdds-server-framework test \
  -Dtest=TestStorageContainerLocationProtocolPB \
  -DskipShade -DskipRecon -DskipDocs

# Secure-mode authentication and SCM service authorization passed:
mvn -pl :ozone-integration-test -am test \
  -Dtest=TestSecureOzoneCluster#testSecureScmAndOmStartupAndAccessControl \
  -Dsurefire.failIfNoSpecifiedTests=false \
  -DskipShade -DskipRecon -DskipDocs \
  -Dmdep.analyze.skip=true

# SCM HA proxy and failover coverage passed:
mvn -pl :ozone-integration-test -am test \
  -Dtest=TestFailoverWithSCMHA \
  -Dsurefire.failIfNoSpecifiedTests=false \
  -DskipShade -DskipRecon -DskipDocs \
  -Dmdep.analyze.skip=true

GitHub Actions CI: https://github.com/echonesis/ozone/actions/runs/32688066691

Generated-by: Codex (GPT-5)

[chihsuan]

Thanks @echonesis +1 LGTM.

[rich7420]

Thanks @echonesis for the patch. Protocol metadata, secure SCM/OM access control, and SCM HA tests passed locally (6 tests, 0 failures or errors). Checkstyle passed.