getSchemaStringType doesn't not respect multibyte charsets

## Description

The maximum varchar length depends on the charset of the table, but the autodetection doesn't take that into account.

https://dev.mysql.com/doc/refman/8.4/en/column-count-limit.html


```
Error 1074 (42000): Column length too big for column 'url' (max = 16383); use BLOB or TEXT instead
```