Make iOS Color default constructor constexpr (#59060)

Summary:
Pull Request resolved: #59060

`UndefinedColor` in the iOS `HostPlatformColor.h` is a namespace-scope `static const Color` built with a non-`constexpr` `Color()`, so every Objective-C++ file that includes the header runs a static initializer before `main`. Make `Color()` `constexpr` (and zero-initialize `uiColorHashValue_`) so it is constant-initialized instead.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D125189249

fbshipit-source-id: 4a2e13df252da37646073bca69b98cb975cbb019

Author: j-piasecki

packages/react-native/ReactCommon/react/renderer/graphics/platform/ios/react/renderer/graphics/HostPlatformColor.h

@@ -26,7 +26,7 @@ struct Color {
   Color(int32_t color);
   Color(const DynamicColor &dynamicColor);
   Color(const ColorComponents &components);
-  Color() : uiColor_(nullptr) {};
+  constexpr Color() : uiColor_(nullptr), uiColorHashValue_(0) {};
   int32_t getColor() const;
   std::size_t getUIColorHash() const;
 

scripts/cxx-api/api-snapshots/ReactAppleDebugCxx.api

@@ -5325,12 +5325,12 @@ struct facebook::react::Bridging<void> {
 }
 
 struct facebook::react::Color {
-  public Color();
   public Color(const facebook::react::ColorComponents& components);
   public Color(const facebook::react::DynamicColor& dynamicColor);
   public Color(int32_t color);
   public bool operator!=(const facebook::react::Color& other) const;
   public bool operator==(const facebook::react::Color& other) const;
+  public constexpr Color();
   public facebook::react::ColorComponents getColorComponents() const;
   public float getChannel(int channelId) const;
   public int32_t getColor() const;

scripts/cxx-api/api-snapshots/ReactAppleFrameworksCxx.api

@@ -8155,12 +8155,12 @@ struct facebook::react::CallbackWithId {
 }
 
 struct facebook::react::Color {
-  public Color();
   public Color(const facebook::react::ColorComponents& components);
   public Color(const facebook::react::DynamicColor& dynamicColor);
   public Color(int32_t color);
   public bool operator!=(const facebook::react::Color& other) const;
   public bool operator==(const facebook::react::Color& other) const;
+  public constexpr Color();
   public facebook::react::ColorComponents getColorComponents() const;
   public float getChannel(int channelId) const;
   public int32_t getColor() const;

scripts/cxx-api/api-snapshots/ReactAppleNewarchCxx.api

@@ -5310,12 +5310,12 @@ struct facebook::react::Bridging<void> {
 }
 
 struct facebook::react::Color {
-  public Color();
   public Color(const facebook::react::ColorComponents& components);
   public Color(const facebook::react::DynamicColor& dynamicColor);
   public Color(int32_t color);
   public bool operator!=(const facebook::react::Color& other) const;
   public bool operator==(const facebook::react::Color& other) const;
+  public constexpr Color();
   public facebook::react::ColorComponents getColorComponents() const;
   public float getChannel(int channelId) const;
   public int32_t getColor() const;

scripts/cxx-api/api-snapshots/ReactAppleReleaseCxx.api

@@ -5318,12 +5318,12 @@ struct facebook::react::Bridging<void> {
 }
 
 struct facebook::react::Color {
-  public Color();
   public Color(const facebook::react::ColorComponents& components);
   public Color(const facebook::react::DynamicColor& dynamicColor);
   public Color(int32_t color);
   public bool operator!=(const facebook::react::Color& other) const;
   public bool operator==(const facebook::react::Color& other) const;
+  public constexpr Color();
   public facebook::react::ColorComponents getColorComponents() const;
   public float getChannel(int channelId) const;
   public int32_t getColor() const;