Compute Stats Incorrect for Binary Columns

I came across an issue when working on HIVE-22674.

The SerDe used for processing binary data tries to auto-detect if the data is in Base-64. It uses org.apache.commons.codec.binary.Base64#isArrayByteBase64 which has two issues:

1. It's slow since it will check if the array is compatible,... and then process the data (examines the array twice)
2. More importantly, this method Tests a given byte array to see if it contains only valid characters within the Base64 alphabet. Currently the method treats whitespace as valid.

https://commons.apache.org/proper/commons-codec/apidocs/org/apache/commons/codec/binary/Base64.html#isArrayByteBase64-byte:A-

The qtest for this feature uses full sentences (which includes spaces) here and therefore it thinks this data is Base-64 and returns an incorrect estimation for size.

This should really not auto-detect Base64 data and instead it should be enabled with a table property.