Remove multiple columns at once in GridBagLayout-Editor

### Description

Hello,

sometimes it can happen that there are to many columns in the GridBagLayout.
This might be due to a component that was spread over multiple columns on purpose or by accident and is now removed or if a component from one layout is copied to another.
Now I would have to delete each column on its own. It would be a big help if this could be done by selecting multiple columns with the selection rectangle or with
Ctrl + Mouse click and then delete them all at once.

Maybe It could also be implemented by adding another row in the properties of the layout that represents the amount of rows and columns and can be edited by text.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a pull request?

No

Start by locating the GridBagLayout-Editor entry point and the existing single-column deletion behavior. Compare the selection-rectangle/Ctrl-click request with the alternative row-and-column properties proposal; done means one chosen interaction reliably removes multiple columns without leaving the layout inconsistent.

Written by the indexing model from the issue text.