Reorganizing tests/ui/issues

Currently there is obsolete `tests/ui/issues`directory in `rustc` test suite which was used to store regression tests in it. Now with the growth of compiler this folder is basically unmanageable, test names don't explain object of testing, and they are not sorted in any way. Nowadays new regression tests are getting into the fitting `tests/ui/`subdir, and my project proposes reorganization of `tests/ui/issues` directory by observing and sorting each test to matching directory.