Add proper support for collations

[altmannmarcelo]

The motivation behind this work is with regards to handling CHAR(x) types.
MySQL has support for multi byte collations, such as utf8mb4 (4 bytes). When handling text fields, specially CHAR we should fill the column width by padding spaces to the right.
When retrieving data from binary log for example, we can extract via TME metadata from the columns, such as column size and ID of collation. The problem relies of the fact that column size is expressed in bytes taking into consideration original collation, for example, for a CHAR(2) column using UTF8MB4_0900_AI_CI the column size will be 8.

Here is one example of TME metadata and BinlogValue::Value for above example for a CHAR(2) insert of value 'A'

get_column_type: MYSQL_TYPE_STRING
metadata: [254, 8] //[0] - Real Column Type, [1] - Column size
charset: 255
value: 'A'

Currently we lack proper collation dictionary to identify Column size as character length.