For now it only has a trivial test (empty) and an all-surrogate test
(Chakma digits) - but at least now all conversions to and from UTF-16
are tested. In particular, there were previously no UTF-32 tests.
Pick-to: 6.2
Change-Id: I9317928a88b9990530126db80e4756b880a364df
Reviewed-by: Ievgenii Meshcheriakov <ievgenii.meshcheriakov@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>