This pull request adds an appearance configuration object to our
settings model and app lib, allowing the control to be rendered
differently depending on its state, and then uses it to add support for
an "unfocused" appearance that the terminal will use when it's not in
focus.
To accomplish this, we isolated the appearance-related settings from
Profile (into AppearanceConfig) and TerminalSettings (into the
IControlAppearance and ICoreAppearance interfaces). A bunch of work was
done to make inheritance work.
The unfocused appearance inherits from the focused one _for that
profile_. This is important: If you define a
defaults.unfocusedAppearance, it will apply all of defaults' settings to
any leaf profile when a terminal in that profile is out of focus.
Specified in #8345Closes#3062Closes#2316
9e83655b08