Blob type Row Hash validation fails between MySQL and Spanner

Hi,

Row Hash validation fails between MySQL and Spanner for Blob fields. The equivalent of Blob type in Spanner is BINARY and the values are as follows:
```
data-validation query -c test_mysql -q 'select blob_column from sample_table where (id < 1814)'
[(b'abbigc',), (b'abbigc',), (b'abbigc',)]
data-validation query -c test_spanner -q 'select cast(blob_column AS String) from sample_table where (id < 1814) and (migration_shard_id="testShardJ")'
[['abbigc'], ['abbigc'], ['abbigc']]
```
Evidently these should match - however DVT appears to use the `encode` function with MySQL blob types and they don't match
```
data-validation query -c test_mysql -q 'select encode(blob_column, "utf-8") from sample_table where (id < 1814)'
[(b'\xaa\xa0.\x8b\xcb\xbb',), (b'\xaa\xa0.\x8b\xcb\xbb',), (b'\xaa\xa0.\x8b\xcb\xbb',)]
```
The recommended approach for casting a MySQL blob to string is:
```
data-validation query -c test_mysql -q 'select convert(blob_column using utf8) from sample_table where (id < 1814)'
[('abbigc',), ('abbigc',), ('abbigc',)]
```
Here is are the parts of the query for Source (MySQL) and Target (Spanner)
```
, encode(t6.blob_column, :encode_1) AS cast__blob_column
FROM sample_table AS t6) AS t5) AS t4) AS t3) AS t2) AS t1) AS t0
WHERE id<1814
12/10/2023 11:27:54 PM-INFO: {'data_client': , 'schema_name': 'mtest', 'table_name': 'sample_table', 'target_query': None}
12/10/2023 11:27:54 PM-INFO: -- ** Target Query ** --
12/10/2023 11:27:54 PM-INFO: WITH t0 AS (
SELECT t6.*, CAST(t6.`blob_column` AS STRING) AS `cast__blob_column`
FROM sample_table t6
```
Sundar Mudupalli