Known unresolved issues after removing VtEngine / adding VT passthrough

[lhecker]

• Reflowing a long line until it wraps results in the cooked read prompt to be misaligned vertically.
• Move the OSC 0 ; P t BEL sequence to WriteWindowTitle and swap the BEL with the ST (ESC \).
• PowerShell on Windows 10 ships with PSReadLine 2.0.0-beta2 which emits SGR 37/40 instead of 39/49. This results in black spaces when typing and there's no good way to fix that.
• Translation of COMMON_LVB_GRID_HORIZONTAL to SGR 53 was dropped and may be reintroduced alongside UNDERSCORE = SGR 4.
• ScrollConsoleScreenBuffer destroys grapheme clusters and extended (VT) attributes and could be translated to DECCRA and DECFRA in the near term. This is important because otherwise vim output may loose its extended attributes during scrolling.
• In cmd: echo ^[[=c (should return a DA3 report like ^[P!|00000000^[\, but we now just get P!|\).
• Original console buffer is not restored when closing a secondary one #17817
• VtIo::Writer::WriteInfos should properly verify the width of each individual character.
• Using SetConsoleActiveScreenBuffer destroys grapheme clusters and extended (VT) attributes. It could be translated to VT pages in the long term.
• A test is missing that ensures that FillConsoleOutputCharacterW results in a CSI n J during the PowerShell shim.
• A test is missing that ensures that PtySignal::ClearBuffer does not result in any VT being generated.
• Port the tests over from Some ScrollConsoleScreenBuffer directions have stopped working correctly #17801
• Incorrect DECRQM for Win32InputMode #17737
• Crash when switching back from the alt buffer #17709
• Some ScrollConsoleScreenBuffer directions have stopped working correctly #17801
• scroll-out in secondary console buffer pollutes main scrollback buffer #17874