Bugfix/9 should use show stream for get table names

[gangtao]

There are couple of fix to support integration with llamaIndex

1. should use text() to wrap queries
2. add missing method get_columns in dialect
3. set default schema (database) to 'default' when it is not specificed

there are more test need to be verified later for

1. schema handling , and add schem in the uri
2. verify following method: from_uri,get_single_table_info,get_table_columns,get_usable_table_names,insert_into_table,run_sql
3. handle those engines introduce by timeplus - stream, external stream etc , now there will be warnings

[jovezhong]

let's add this empty line back. Minor thing but will make our future rebase/cherrypick a bit easier

[jovezhong]

(Jove Github Bot) added it to the current sprint.

[jovezhong]

(Jove Github Bot) moved this ticket out of the GitHub project(up to 1200 tickets for one project).