[test] merge common stuff in main.hh

The original test_common.hh has been merged with test_main.cxx and
test_main_debug.cxx into main.hh. From now on one only has to
    #include <dune/stuff/test/main.hh>
which already provides a main(). If one wishes to catch exceptions (for
debug output, one can define
    -DDUNE_STUFF_TEST_MAIN_CATCH_EXCEPTIONS=1
[common.exception] whitespace
[test.main] whitespace
[test.main] introduce DUNE_STUFF_TEST_MAIN_ENABLE_INFO_LOGGING
[test] update deprecation warnings