This pull request converts the following JSON deserializers to use the
new JSON deserializer pattern:
* Profile
* Command
* ColorScheme
* Action/Args
* GlobalSettings
* CascadiaSettingsSerialization
This is the completion of a long-term JSON refactoring that makes our
parser and deserializer more type-safe and robust. We're finally able to
get rid of all our manual enum conversion code and unify JSON conversion
around _types_ instead of around _keys_.
I've introduced another file filled with template specializations,
TerminalSettingsSerializationHelpers.h, which comprises a single unit
that holds all of the JSON deserializers (and eventually serializers)
for every type that comes from TerminalApp or TerminalSettings.
I've also moved some types out of Profile and GlobalAppSettings into a
new SettingsTypes.h to improve settings locality.
This does to some extent constitute a breaking change for already-broken
settings. Instead of parsing "successfully" (where invalid values are
null or 0 or unknown or unset), deserialization will now fail when
there's a type mismatch. Because of that, some tests had to be removed.
While I was on a refactoring spree, I removed a number of helpless
helpers, like GetWstringFromJson (which converted a u8 string to an
hstring to make a wstring out of its data pointer :|) and
_ConvertJsonToBool.
In the future, we can make the error types more robust and give them
position and type information such that a conformant application can
display rich error information ("line 3 column 3, I expected a string,
you gave me an integer").
Closes#2550.
