[IcebergIO] Wrap nullable Logger args for Java 17 Checker Framework

Raising the Java floor to 17 routes IcebergIO through a compile path where Beam's org.slf4j.Logger nullness suppression (skipUses) is not applied, so two latent Logger.info(@nullable) calls hard-error under the NullnessChecker. Wrap the nullable args in String.valueOf to make them @nonnull.

Author: peterphitran

sdks/java/io/iceberg/src/main/java/org/apache/beam/sdk/io/iceberg/AddFiles.java

@@ -185,7 +185,8 @@ public PCollectionRowTuple expand(PCollection<String> input) {
 
     if (!Strings.isNullOrEmpty(locationPrefix)) {
       LOG.info(
-          "AddFiles configured to build partition metadata after the prefix: '{}'", locationPrefix);
+          "AddFiles configured to build partition metadata after the prefix: '{}'",
+          String.valueOf(locationPrefix));
     }
 
     PCollectionTuple dataFiles =

sdks/java/io/iceberg/src/main/java/org/apache/beam/sdk/io/iceberg/CreateReadTasksDoFn.java

@@ -68,7 +68,7 @@ public void process(
       if (!DataOperations.APPEND.equals(snapshot.getOperation())) {
         LOG.info(
             "Skipping non-append snapshot of operation '{}'. Sequence number: {}, id: {}",
-            snapshot.getOperation(),
+            String.valueOf(snapshot.getOperation()),
             snapshot.getSequenceNumber(),
             snapshot.getSnapshotId());
       }