Select all text on TAB focus for sinle text field

Multi-line text field keeps it's previous behavior.

438632: [Text] Focussing a text field by TAB does not select all text
https://bugs.eclipse.org/bugs/show_bug.cgi?id=438632

Change-Id: I218572a5cbe133745a258f9df203fe9ca1fc55b1
Signed-off-by: Ivan Furnadjiev <ivan@eclipsesource.com>