feat: add binary row serializers and blob implementation

[lszskye]

Purpose

Introduce serialization infrastructure for Paimon's binary row format, including BinaryRowSerializer, BinarySerializerUtils, RowCompactedSerializer, and the Blob implementation.

Changes

BinaryRowSerializer

• Serializes/deserializes BinaryRow

BinarySerializerUtils

• Utility class for converting InternalRow, InternalArray, InternalMap into their binary counterparts (BinaryRow, BinaryArray, BinaryMap)

RowCompactedSerializer

• Compact serialization format for InternalRow, using bitset-based null tracking and variable-length integer encoding
• Provides SerializeToBytes() / Deserialize() for row-level serialization

Blob

• Implementation of Blob class for managing blob descriptors and blob data

Tests

• BinaryRowSerializerTest
• BinarySerializerUtilsTest
• RowCompactedSerializerTest

[leaves12138]

Thanks for the PR. I found two blockers that should be fixed before merge: one compile-time missing include and one moved-from unique_ptr dereference risk in Blob construction.

[leaves12138]

This header is not present in the PR head or the current base branch, so including paimon/common/utils/var_length_int_utils.h makes this code fail to compile. Please add the missing utility header/implementation or switch to an existing varint helper.

[leaves12138]

This passes std::move(descriptor) and descriptor->Uri() in the same function call. The argument evaluation order is unspecified, so descriptor->Uri() may run after the unique_ptr has been moved from and become null. Please capture the URI before moving descriptor; the same pattern below in FromDescriptor needs the same fix.