Adds support for `win32-input-mode` to conhost, conpty, and the Windows
Terminal.
* The shared `terminalInput` class supports sending these sequences when
a VT client application requests this mode.
* ConPTY supports synthesizing `INPUT_RECORD`s from the input sent to it
from a terminal
* ConPTY requests this mode immediately on startup (if started with a
new flag, `PSEUDOCONSOLE_WIN32_INPUT_MODE`)
* The Terminal now supports sending this input as well, when conpty asks
for it.
Also adds a new ConPTY flag `PSEUDOCONSOLE_WIN32_INPUT_MODE` which
requests this functionality from conpty, and the Terminal requests this
by default.
Also adds `experimental.input.forceVT` as a global setting to let a user
opt-out of this behavior, if they don't want it / this ends up breaking
horribly.
## Validation Steps Performed
* played with this mode in vtpipeterm
* played with this mode in Terminal
* checked a bunch of scenarios, as outlined in a [comment] on #4999
[comment]: https://github.com/microsoft/terminal/issues/4999#issuecomment-628718631
References #4999: The megathread
References #5887: The spec
Closes#879Closes#2865Closes#530Closes#3079Closes#1119Closes#1694Closes#3608Closes#4334Closes#4446
f32761849f