When in raw mode, go to level 2, but use level 1 for cooked
so that we don't obfuscate ctrl-c.
A consequnce of this is that CTRL-C is now reported to the app
as CTRL-lowercase-c where we previously reported as CTRL-uppercase-C.
Made a note of the breaking nature of this change in a new changelog
file.
Fixed recognizing SHIFT-TAB
refs: https://github.com/wez/wezterm/issues/2511
It's been replaced with an opaque termwiz error type instead.
This is a bit of a more conservative approach than that in (refs: #407)
and has less of an impact on the surrounding code, which appeals to
me from a maintenance perspective.
refs: #406
refs: #407
