IMPALA-15118: Copy ByteBuffers for partitionList_

IcebergContentFileStore.fromThrift() didn't copy the contents
of ByteBuffers when filling partitionList_.
Thrift's binary handling in Java is special as the ByteBuffer
object in deserialized Thrift object can still reference the
transport buffer. Keeping the reference to that can almost
double the size of IcebergContentFileStore in the coordinator.

Another issue fixed is that partitionMap_ and partitionList_ did
not share the ByteBuffers  after fromThrift()

Improvement for test table with 1M files, 25K partitions:
665MB->389MB

Change-Id: Ib39940dd64aadcb094b099e3863dd42c22afc2b8
Reviewed-on: http://gerrit.cloudera.org:8080/24515
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

fe/src/main/java/org/apache/impala/catalog/IcebergContentFileStore.java

diff --git a/fe/src/main/java/org/apache/impala/catalog/IcebergContentFileStore.java b/fe/src/main/java/org/apache/impala/catalog/IcebergContentFileStore.java
index 18dec4c..ae2f7ec 100644
--- a/fe/src/main/java/org/apache/impala/catalog/IcebergContentFileStore.java
+++ b/fe/src/main/java/org/apache/impala/catalog/IcebergContentFileStore.java
@@ -695,10 +695,13 @@
     ret.hasParquet_ = tFileStore.isSetHas_parquet() ? tFileStore.isHas_parquet() : false;
     ret.missingFiles_ = tFileStore.isSetMissing_files() ?
         new HashSet<>(tFileStore.getMissing_files()) : Collections.emptySet();
+    // Call copyBinary to avoid referencing the whole transport buffer in ByteBuffers.
     ret.partitionList_ = tFileStore.isSetPartitions() ?
-        tFileStore.getPartitions() : new ArrayList<>();
-    ret.partitionMap_ = tFileStore.isSetPartitions() ?
-        convertPartitionListToMap(tFileStore.getPartitions()) : new HashMap<>();
+        tFileStore.getPartitions().stream()
+            .map(org.apache.thrift.TBaseHelper::copyBinary)
+            .collect(Collectors.toList())
+        : new ArrayList<>();
+    ret.partitionMap_ = convertPartitionListToMap(ret.partitionList_);
     return ret;
   }
 
@@ -720,7 +723,7 @@
     Preconditions.checkState(partitionList != null);
     ImmutableMap.Builder<ByteBuffer, Integer> builder = ImmutableMap.builder();
     for (int i = 0; i < partitionList.size(); ++i) {
-      builder.put(org.apache.thrift.TBaseHelper.copyBinary(partitionList.get(i)), i);
+      builder.put(partitionList.get(i), i);
     }
     return builder.build();
   }