[#11138][#11137] refactor(iceberg-rest): federation handling via FederatedCatalogWrapper subclass

[roryqi]

What changes were proposed in this pull request?

Federation logic in CatalogWrapperForREST was implemented as scattered
instanceof RESTCatalog / isRESTCatalog() short-circuits across the class.
This PR refactors them into polymorphic dispatch and fixes the missing
registerTable federation path:

• Add FederatedCatalogWrapper extends CatalogWrapperForREST that overrides the
  operations needing federation-aware behavior: createTable, loadTable,
  updateTable, registerTable, and buildCatalogConfigToClients.
• Add a CatalogWrapperForREST.create(...) factory that returns the federated
  subclass when the backend is rest, and wire IcebergCatalogWrapperManager
  to it.
• Add registerTableInternal, mirroring loadTableInternal, so federated
  registerTable extracts FileIO-derived client config and credential fields
  from the remote catalog's table.io() (previously dropped). ([Subtask] Add federation FileIO-property-extraction to registerTable #11137)
• Remove the now-dead instanceof/isRESTCatalog() branches from the base
  class (createTable, loadTable, updateTable, shouldGenerateCredential),
  and make buildCatalogConfigToClients an overridable instance method backed by
  a shared filterCatalogConfigForClients helper.

Why are the changes needed?

Adding a new federated operation required remembering to add a corresponding
instanceof check; nothing in the type system enforced it. The missing
registerTable federation handling was a direct bug from this pattern: a
federated registerTable returned a LoadTableResponse without the
FileIO-derived properties and credential fields that createTable/loadTable
include. Polymorphic dispatch removes the foot-gun and fixes the bug.

Fix: #11138
Fix: #11137

Does this PR introduce any user-facing change?

No. Federated registerTable responses now include the FileIO/credential client
config they should have included before; no API or property-key changes.

How was this patch tested?

./gradlew :iceberg:iceberg-rest-server:test -PskipITs (full module unit suite
green), plus new unit tests:

• testCreateReturnsFederatedWrapperForRestBackend
• testCreateReturnsBaseWrapperForNonRestBackend
• testFederatedRegisterTableIncludesFileIo

Existing buildCatalogConfigToClients tests were updated to exercise the
polymorphic source selection and the shared filter helper.

🤖 Generated with Claude Code

[github-actions]

Code Coverage Report

Overall Project	66.81% +0.03%	🟢
Files changed	73.14%	🟢

Module	Coverage
aliyun	1.72%	🔴
api	46.82%	🟢
authorization-common	85.96%	🟢
aws	3.66%	🔴
azure	2.47%	🔴
catalog-common	10.04%	🔴
catalog-fileset	80.33%	🟢
catalog-glue	66.08%	🟢
catalog-hive	79.55%	🟢
catalog-jdbc-clickhouse	80.02%	🟢
catalog-jdbc-common	45.31%	🟢
catalog-jdbc-doris	80.28%	🟢
catalog-jdbc-hologres	54.03%	🟢
catalog-jdbc-mysql	79.23%	🟢
catalog-jdbc-oceanbase	78.38%	🟢
catalog-jdbc-postgresql	82.29%	🟢
catalog-jdbc-starrocks	78.51%	🟢
catalog-kafka	77.01%	🟢
catalog-lakehouse-generic	44.89%	🟢
catalog-lakehouse-hudi	79.1%	🟢
catalog-lakehouse-iceberg	85.66%	🟢
catalog-lakehouse-paimon	79.29%	🟢
catalog-model	77.72%	🟢
cli	44.51%	🟢
client-java	77.91%	🟢
common	49.99%	🟢
core	82.49%	🟢
filesystem-hadoop3	76.97%	🟢
flink	0.0%	🔴
flink-common	41.2%	🟢
flink-runtime	0.0%	🔴
gcp	14.12%	🔴
hadoop-common	10.39%	🔴
hive-metastore-common	53.26%	🟢
iceberg-common	56.75%	🟢
iceberg-rest-server	72.52% +0.09%	🟢
idp-basic	85.99%	🟢
integration-test-common	0.0%	🔴
jobs	66.17%	🟢
lance-common	20.83%	🔴
lance-rest-server	60.27%	🟢
lineage	53.02%	🟢
optimizer	82.95%	🟢
optimizer-api	21.95%	🔴
server	85.73%	🟢
server-common	73.13%	🟢
spark	32.79%	🔴
spark-common	39.75%	🔴
trino-connector	39.44%	🔴

Files

Module	File	Coverage
iceberg-rest-server	FederatedCatalogWrapper.java	87.5%	🟢
	CatalogWrapperForREST.java	73.3%	🟢
	IcebergCatalogWrapperManager.java	69.81%	🟢