fix some deprecations
various deprecations, especially our own usage of deprecated APIs in this package
- remove few remaining references to, uses of io.stdout
- suppress deprecation warnings when initializing deprecated `utils.io.std*`
- globalipapp.StreamProxy is now totally unused
- one missing traitlets 4.2 API in core.formatters
- get gui keys from pt_inputhooks instead of deprecated lib.inputhook
- stop passing deprecated color_scheme to Pdb
- nt.assert_equals in test_latextools
