MySQL/MariaDB: return max length for text columns using `CHARACTER_MAXIMUM_LENGTH`.
Tests:
* add an integration test: `TestGetColumnsLength`
* update `TestSyncTable3` since `TableInfo` isn't able to provide the column size
Co-authored-by: Pierre-Louis Bonicoli <pierre-louis.bonicoli@libregerbil.fr>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/xorm/xorm/pulls/2133
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Pierre-Louis Bonicoli <pilou@noreply.gitea.io>
Co-committed-by: Pierre-Louis Bonicoli <pilou@noreply.gitea.io>