Intellisense does not list extension fields in RequestFilterFields for report extensions

[NKarolak]

1. Describe the bug
On adding RequestFilterFields within a report extension, IntelliSense does not list extension fields.

2. To Reproduce

1. Create a new app. Extend table Work Center with one or more new fields.

2. Add a report extension object:

reportextension 50000 NewCalcWorkCenterCalendar extends "Calculate Work Center Calendar"
{
    dataset
    {
        modify("Work Center")
        {
            RequestFilterFields = <intellisense here>;
        }
    }
}

3. After RequestFilterFields =, run IntelliSense and search for your new fields created in step 1.

3. Expected behavior
Extension fields should be listed.

4. Actual behavior
InstelliSense lists only base fields.
However, we can still add the required fields without IntelliSense.

5. Versions:
AL Language: v13.0.1027618, runtime 13.0.
Internal work item: AB#554259