Renaming a column to an existing column should show a warning to users

As a user, I want to be warned, if the action I am taking may have unforeseen consequences, such as deleting or overwriting an existing column.
In data prep, columns need to have unique names. Selecting an already existing name triggers the warning.

Acceptance Criteria

• The user rename a column using a name that is already existing and a warning is displayed
• The warning disappears, as soon as the user picks a unique name
• The warning appears contextually and it spans the width of the column
• Warning text: A column with the same name already exists. Pick a new name, or click “Apply” to overwrite.
• Clicking [Apply] overwrites the existing column
• Clicking [Cancel] will not change the name of the column.