[REG 3.3 -> 3.4] "Name" column in "Locals and Expressions" is too narrow

1. Create a new Qt Quick UI project using component set "Qt Quick 2.3".
2. Start debugging this.
   You'll see the "Locals and Expressions" view which displays the items. The "Name" column is too narrow:
   
3. Double-click the name of of the first item.
   The column will resize to the correct width:
   

"Locals and Expressions" view should use the correct width from the beginning. Double clicking an item should then open it's sub-tree. This used to work correctly in Creator 3.3.

Found by Squish test tst_qml_js_console.