Reduce usage of Json::Value throughout Terminal.Settings.Model (#11184)

This commit reduces the code surface that interacts with raw JSON data,
reducing code complexity and improving maintainability.
Files that needed to be changed drastically were additionally
cleaned up to remove any code cruft that has accrued over time.

In order to facility this the following changes were made:
* Move JSON handling from `CascadiaSettings` into `SettingsLoader`
  This allows us to use STL containers for data model instances.
  For instance profiles are now added to a hashmap for O(1) lookup.
* JSON parsing within `SettingsLoader` doesn't differentiate between user,
  inbox and fragment JSON data, reducing code complexity and size.
  It also centralizes common concerns, like profile deduplication and
  ensuring that all profiles are assigned a GUID.
* Direct JSON modification, like the insertion of dynamic profiles into
  settings.json were removed. This vastly reduces code complexity,
  but unfortunately removes support for comments in JSON on first start.
* `ColorScheme`s cannot be layered. As such its `LayerJson` API was replaced
  with `FromJson`, allowing us to remove JSON-based color scheme validation.
* `Profile`s used to test their wish to layer using `ShouldBeLayered`, which
  was replaced with a GUID-based hashmap lookup on previously parsed profiles.

Further changes were made as improvements upon the previous changes:
* Compact the JSON files embedded binary, saving 28kB
* Prevent double-initialization of the color table in `ColorScheme`
* Making `til::color` getters `constexpr`, allow better optimizations

The result is a reduction of:
* 48kB binary size for the Settings.Model.dll
* 5-10% startup duration
* 26% code for the `CascadiaSettings` class
* 1% overall code in this project

Furthermore this results in the following breaking changes:
* The long deprecated "globals" settings object will not be detected and no
  warning will be created during load.
* The initial creation of a new settings.json will not produce helpful comments.

Both cases are caused by the removal of manual JSON handling and the
move to representing the settings file with model objects instead

## PR Checklist
* [x] Closes #5276
* [x] Closes #7421
* [x] I work here
* [x] Tests added/passed

## Validation Steps Performed

* Out-of-box-experience is identical to before ✔️
  (Except for the settings.json file lacking comments.)
* Existing user settings load correctly ✔️
* New WSL instances are added to user settings ✔️
* New fragments are added to user settings ✔️
* All profiles are assigned GUIDs ✔️

.github/actions/spelling/expect/expect.txt

@@ -557,6 +557,7 @@ DECSTR
 DECSWL
 DECTCEM
 Dedupe
+deduplicate
 deduplicated
 DEFAPP
 DEFAULTBACKGROUND
@@ -784,6 +785,7 @@ FINDSTRINGEXACT
 FINDUP
 FIter
 FIXEDCONVERTED
+FIXEDFILEINFO
 Flg
 flyout
 fmodern
@@ -1992,6 +1994,7 @@ resx
 retval
 rfa
 rfc
+rfid
 rftp
 rgb
 rgba

README.md

@@ -289,6 +289,7 @@ If you would like to ask a question that you feel doesn't warrant an issue
 * You must [enable Developer Mode in the Windows Settings
   app](https://docs.microsoft.com/en-us/windows/uwp/get-started/enable-your-device-for-development)
   to locally install and run Windows Terminal
+* You must have [PowerShell 7 or later](https://github.com/PowerShell/PowerShell/releases/latest) installed
 * You must have the [Windows 10 1903
   SDK](https://developer.microsoft.com/en-us/windows/downloads/windows-10-sdk)
   installed

src/cascadia/LocalTests_SettingsModel/CommandTests.cpp

@@ -43,12 +43,6 @@ namespace SettingsModelLocalTests
         TEST_METHOD(TestLayerOnAutogeneratedName);
 
         TEST_METHOD(TestGenerateCommandline);
-
-        TEST_CLASS_SETUP(ClassSetup)
-        {
-            InitializeJsonReader();
-            return true;
-        }
     };
 
     void CommandTests::ManyCommandsSameAction()

src/cascadia/LocalTests_SettingsModel/JsonTestClass.h

@@ -7,44 +7,34 @@ Module Name:
 
 Abstract:
 - This class is a helper that can be used to quickly create tests that need to
-  read & parse json data. Test classes that need to read JSON should make sure
-  to derive from this class, and also make sure to call InitializeJsonReader()
-  in the TEST_CLASS_SETUP().
+  read & parse json data.
 
 Author(s):
     Mike Griese (migrie) August-2019
 --*/
 
+#pragma once
+
 class JsonTestClass
 {
 public:
-    void InitializeJsonReader()
-    {
-        _reader = std::unique_ptr<Json::CharReader>(Json::CharReaderBuilder::CharReaderBuilder().newCharReader());
-    };
-
-    void InitializeJsonWriter()
+    static Json::Value VerifyParseSucceeded(const std::string_view& content)
     {
-        _writer = std::unique_ptr<Json::StreamWriter>(Json::StreamWriterBuilder::StreamWriterBuilder().newStreamWriter());
-    }
+        static const std::unique_ptr<Json::CharReader> reader{ Json::CharReaderBuilder::CharReaderBuilder().newCharReader() };
 
-    Json::Value VerifyParseSucceeded(std::string content)
-    {
         Json::Value root;
         std::string errs;
-        const bool parseResult = _reader->parse(content.c_str(), content.c_str() + content.size(), &root, &errs);
+        const bool parseResult = reader->parse(content.data(), content.data() + content.size(), &root, &errs);
         VERIFY_IS_TRUE(parseResult, winrt::to_hstring(errs).c_str());
         return root;
     };
 
-    std::string toString(const Json::Value& json)
+    static std::string toString(const Json::Value& json)
     {
+        static const std::unique_ptr<Json::StreamWriter> writer{ Json::StreamWriterBuilder::StreamWriterBuilder().newStreamWriter() };
+
         std::stringstream s;
-        _writer->write(json, &s);
+        writer->write(json, &s);
         return s.str();
     }
-
-protected:
-    std::unique_ptr<Json::CharReader> _reader;
-    std::unique_ptr<Json::StreamWriter> _writer;
 };

src/cascadia/LocalTests_SettingsModel/KeyBindingsTests.cpp

@@ -59,12 +59,6 @@ namespace SettingsModelLocalTests
 
         TEST_METHOD(TestGetKeyBindingForAction);
         TEST_METHOD(KeybindingsWithoutVkey);
-
-        TEST_CLASS_SETUP(ClassSetup)
-        {
-            InitializeJsonReader();
-            return true;
-        }
     };
 
     void KeyBindingsTests::KeyChords()