Improve table/column editing UI flow

[juliushaertl]

I noticed that we have 3 dialogs that are all reachable from different positions currently.

• Table details (from the navigation menu)
• Edit columns (from the table 3 dots menu)
• Add columns (from the table 3 dots menu)

I think it would be nice to either unify parts of those or at least provide shortcuts.

Proposal 1: Move the edit columns dialog into the table details. This would allow to change all table metadata and the column layout in one view that could be opened through the navigation and main table view then.

Proposal 2: Add a button to add new columns within the edit columns dialog. That way there is no need to close the dialog to open another one.

cc @nimishavijay @jancborchardt