Extend input_test example for better debug capabilities

[penguinolog]

• Extra logging in raw display subclasses
• Better type annotations
• sigwinch_handler - use signal.SIGWINCH value as default

Checklist

• I've ensured that similar functionality has not already been implemented
• I've ensured that similar functionality has not earlier been proposed and declined
• I've branched off the master or python-dual-support branch
• I've merged fresh upstream into my branch recently
• I've ran tox successfully in local environment
• I've included docstrings and/or documentation and/or examples for my code (if this is a new feature)

Related #700

[coveralls]

Pull Request Test Coverage Report for Build 7260167987

• 2 of 14 (14.29%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.09%) to 70.992%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
urwid/_win32_raw_display.py	0	1	0.0%
urwid/_posix_raw_display.py	1	3	33.33%
urwid/_raw_display_base.py	1	10	10.0%

Files with Coverage Reduction	New Missed Lines	%
urwid/_posix_raw_display.py	1	12.5%

Totals
Change from base Build 7254187795:	-0.09%
Covered Lines:	7589
Relevant Lines:	10788

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💛 - Coveralls