ENH: Unify error/warning testing

CHECK_ERROR_MSG and CHECK_WARNING_MSG are used to check the content of error and warning messages. Error and warning code is often overlooked during testing. Over the years, these two macros have been refined to increase their utility. Tests that use the macros defined their own interpretations. Three different API's have been used in the macros.

This patch replaces the CHECK_ERROR_MSG and CHECK_WARNING_MSG macros with methods for vtkTest::ErrorObserver. All tests that used the CHECK macros in one form or another have been updated to use the CheckErrorMessage and CheckWarningMessage methods.