MySQL client data type mapping rework - fixes #1239

[BillyYccc]

Motivation:

This PR reworks the MySQL client data type mapping part, with fixes to #1239

Modifications:

1. move checking unsigned & binary flags from data type codec to column definition parsing phase which can avoid checking those flags at row value decoding phase for each prepared statement executing and improve some performance
2. add dedicated unsigned
   numeric & binary datatypes to the DataType enum so that the data type codec can use them to decode row values
3. make some changes to the MySQL JDBCType mapping
   FLOAT: JDBCType.REAL-> JDBCType.FLOAT
   CHAR,ENUM: JDBCType.VARCHAR -> JDBCType.CHAR
   BINARY: JDBCType.VARCHAR -> JDBCType.BINARY
   VARBINARY: JDBCType.VARCHAR -> JDBCType.VARBINARY
   TINY_TEXT: JDBCType.BLOB -> JDBCType.CLOB
   TEXT: JDBCType.BLOB -> JDBCType.CLOB
   MEDIUM_TEXT: JDBCType.BLOB -> JDBCType.CLOB
   LONG_TEXT: JDBCType.BLOB -> JDBCType.CLOB

[vietj]

thanks @BillyYccc !