Fix WSL support: filter-out SI/SO in case of WSL

[penguinolog]

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)

Fix: #264

[coveralls]

Pull Request Test Coverage Report for Build 7015530099

• 2 of 4 (50.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.01%) to 74.15%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
urwid/raw_display.py	2	4	50.0%

Files with Coverage Reduction	New Missed Lines	%
urwid/raw_display.py	1	18.19%

Totals
Change from base Build 7015514000:	-0.01%
Covered Lines:	7519
Relevant Lines:	10284

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💛 - Coveralls

[wardi]

IIRC SO/SI are used for some graphics characters when not in UTF-8 mode:
https://github.com/urwid/urwid/blob/671ba131114cf86e79ebf76cd10d01c553e6054a/urwid/escape.py#L47C1-L47C55

instead of stripping these control characters at the last minute it's probably better to disable all the graphics character handling before sending it to the screen (graphics all get converted to ? or some other placeholder on WSL)

[penguinolog]

IIRC SO/SI are used for some graphics characters when not in UTF-8 mode:
https://github.com/urwid/urwid/blob/671ba131114cf86e79ebf76cd10d01c553e6054a/urwid/escape.py#L47C1-L47C55

instead of stripping these control characters at the last minute it's probably better to disable all the graphics character handling before sending it to the screen (graphics all get converted to ? or some other placeholder on WSL)

WSL is in UTF8. I validated on real windows.
All characters displayed correctly (added also Cyrillic raw as sample):

[penguinolog]

rebased from latest master

[penguinolog]

Validated that changes are not needed for curses display under WSL