ContentAssistant does work right with real Ibmi-DB2 SQL-Tables (metadatasource=0/1 and naming=system)

#### System information:
- Operating system (distribution) and version === Microsoft Windows 10 Enterprise - Version 10.0.19042 Build 19042
- DBeaver version === Version 21.0.3.202104181339 - Released 19 April 2021
- Additional extensions === NO, standalone DBeaver instance - Same behaviour in the Eclipse IDE.

#### Connection specification:
- Database name and version === Ibmi DB2 V7R4 - Latest TR
- Driver name === DB2 iSeries/AS 400 - net.sf.jt400:jt400:RELEASE - Version 10.6
- Do you use tunnels or proxies (SSH, SOCKS, etc) === NO

#### Describe the problem you're observing:
* DBeaver is really a **very very good tool** to work with databases. **Many thanks !**

* I read thru the docs and issues, but did not see what I'm doing wrong.

* I would like to actively contribute to find solutions/document/test because we are currently moving to 'real' SQL-Tables instead of PFs and LFs (legacy physical and logical files) and the issues have mostly to do with these new tables.

* I can use the Ibmi system I develop on to carry out tests. I cloned the repo to start debugging.

* I think all the issues have to do with these driver settings :
* naming="system" meaning that the DB-objects are searched in a list of schemas (Libraries) instead of only the one set with SET SCHEMA
* metadatasource="0" (Retrieve Object Information) or "1" (SQL stored procedures) or "-1" (??)

* Just wanna give an overview of the issues here. I can split them apart later on into separate bugReports for easier handling and supply more details.

* Issue 1 : Table properties do not show ANY columns for real SQL-Tables :
* 
* Note that an SQL-Script shows the right metadata

* Issue 2 : Table properties for legacy PFs do not show column descriptions when metadatasource="1"
* 
* 

* Issue 3 : Content assistant in SQL script does only find tables when a schema is set (is against naming=system)

* 
* 

* Issue 4 : Content assistant in SQL script does not show columns for real SQL-Tables

* does not show for real SQL-Tables

* does show right for legacy PFs

#### Steps to reproduce, if exist:

#### Include any warning/errors/backtraces from the logs