Run some wxTextCtrl unit test cases for single and multi-line controls.

Some of the tests that were previously ran for single or multi-line controls
only actually apply to both of them, so run them for both kinds of control to
test that both of them work correctly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71307 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775