[SPARK-14016][SQL] Support high-precision decimals in vectorized parquet reader

## What changes were proposed in this pull request?

This patch adds support for reading `DecimalTypes` with high (> 18) precision in `VectorizedColumnReader`

## How was this patch tested?

1. `VectorizedColumnReader` initially had a gating condition on `primitiveType.getDecimalMetadata().getPrecision() > Decimal.MAX_LONG_DIGITS()` that made us fall back on parquet-mr for handling high-precision decimals. This condition is now removed.
2. In particular, the `ParquetHadoopFsRelationSuite` (that tests for all supported hive types -- including `DecimalType(25, 5)`) fails when the gating condition is removed (https://github.com/apache/spark/pull/11808) and should now pass with this change.

Author: Sameer Agarwal <sameer@databricks.com>

Closes #11869 from sameeragarwal/bigdecimal-parquet.

sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedColumnReader.java

@@ -262,6 +262,11 @@ public class VectorizedColumnReader {
             Binary v = dictionary.decodeToBinary(dictionaryIds.getInt(i));
             column.putLong(i, CatalystRowConverter.binaryToUnscaledLong(v));
           }
+        } else if (DecimalType.isByteArrayDecimalType(column.dataType())) {
+          for (int i = rowId; i < rowId + num; ++i) {
+            Binary v = dictionary.decodeToBinary(dictionaryIds.getInt(i));
+            column.putByteArray(i, v.getBytes());
+          }
         } else {
           throw new NotImplementedException();
         }
@@ -368,6 +373,14 @@ public class VectorizedColumnReader {
           column.putNull(rowId + i);
         }
       }
+    } else if (DecimalType.isByteArrayDecimalType(column.dataType())) {
+      for (int i = 0; i < num; i++) {
+        if (defColumn.readInteger() == maxDefLevel) {
+          column.putByteArray(rowId + i, data.readBinary(arrayLen).getBytes());
+        } else {
+          column.putNull(rowId + i);
+        }
+      }
     } else {
       throw new NotImplementedException("Unimplemented type: " + column.dataType());
     }

sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedParquetRecordReader.java

@@ -220,10 +220,6 @@ public class VectorizedParquetRecordReader extends SpecificParquetRecordReaderBa
           originalTypes[i] != OriginalType.INT_8 && originalTypes[i] != OriginalType.INT_16) {
         throw new IOException("Unsupported type: " + t);
       }
-      if (originalTypes[i] == OriginalType.DECIMAL &&
-          primitiveType.getDecimalMetadata().getPrecision() > Decimal.MAX_LONG_DIGITS()) {
-        throw new IOException("Decimal with high precision is not supported.");
-      }
       if (primitiveType.getPrimitiveTypeName() == PrimitiveType.PrimitiveTypeName.INT96) {
         throw new IOException("Int96 not supported.");
       }