Unified Add Layer: when using OgrConnection, embed the list of tables in the data source manager dialog

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 17002

Redmine category:gui

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Data source Manager --> Vector --> Database
Connect a database (i tried PG connection) and add layers
Instead of a new dialog that opens, could be nice tio have the liste of tables embedded in the Data Source Manager dialog, the same way it's done for other providers. Would even be better if the table that displays the information of the retrieved layers could have the same columns shown in the other tabs

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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The Vector tab is in fact the OGR provider that can connect to several data databases (postgis included), on the other hand the postgis provider implemented in QGIS is more feature rich and I'd be in favour of removing the option to connect to postgis via OGR from the Vector dialog instead of having two different ways to add a postgis layer, that is just confusing for the user.