Text tool: Clicking in the font-family combobox should select the font-family, so typing replaces it
Migrated from: https://bugs.launchpad.net/inkscape/+bug/167565
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- Create a text
- Click in the font family combobox
#### What happened?
The font family is not selected, and the cursor is moved where I clicked.
#### What should have happened?
The font family is selected, so it can be overtyped. It's probably a rare use case to change only a part of a font's name, and in that case, a user can click again.
Double-clicking only selects the current "word" of the font family.
By changing this, it would be consistent with
* Giving focus to the font family by Alt+X
* Other software, such as MS Word
Should probably be changed for the other combo boxes in the text tool as well.
#### Inkscape Version and Operating System:
* Inkscape Version: 1.1-dev (6b4d57f, 2020-04-01)
* Operating System: Windows 10
* Operating System version: 10.0.18362
issue