Update textfield readonly style (Valo)

Make readonly textfields show better inside panels for instance (so
that they look different from normal textfields).

Change-Id: If2b9b810a5bf0d7388563ea1d7560bbf1b9f149a
Valo reports theme version wrong in debug window (#14338)

Change-Id: I15f35e2c1e5e61027fc4fca6593f24f1112624c7