This corrects an issue where the mode byte of the DCS sequence was
discarded from the DcsHook, making it impossible to know what sequence
is being activated.
So far this hasn't come up as these sequences are relatively rare,
but in looking at sixel parsing I noticed the error.
This commit changes the behavior on Windows:
* If $TERM is set and the `terminfo` crate is able to
successfully initialize and locate a terminfo database (this also
requires that $TERMINFO be set in the environment), then we'll
use the `TerminfoRenderer` instead of the `WindowsConsoleRenderer`
* If $TERM is set to `xterm-256color` and no terminfo database was
found, use our modern compiled-in copy (look in the `termwiz/data/`
directory for the source and compiled version of this) and use
the `TerminfoRenderer`.
* Otherwise use the `WindowsConsoleRenderer`.
In practice, this allows termwiz apps to opt in to features such as
true color support on Windows 10 build 1903 an later by setting their
`TERM=xterm-256color`. This happens to be the default behavior when
`ssh`ing in to a windows host via `wezterm`.
You can see the truecolor mode get applied by running this example:
```
cargo run --example widgets_basic --features widgets
```
with TERM set as above the background region that is painted by the app
will be a blueish/purplish color, but with it unset or set to something
invalid, it will fall back to black.
I'd like to eventually make termwiz assume the equivalent configuration
to `TERM=xterm-256color` by default on Windows 10 build 1903 and later,
but it's worth getting some feedback on how this works for clients such
as `streampager`.
cc: @quark-zju and @markbt
