Fix TextInput placeholder font when using custom fonts. Fixes #4600

Summary:
When using a TextInput with a custom font, the placeholder didn't use that font. This is because ReactTextInputManager didn't use ReactFontManager to create the TypeFace which handles custom fonts.

**Test plan**
Tested in UI explorer by reproducing the bug with and testing that the custom font gets applied properly after the fix.
``` js
<TextInput
  placeholder="Hello"
  style={{ fontFamily: 'notoserif' }}
/>
```
Closes #12000

Reviewed By: hramos

Differential Revision: D4443713

fbshipit-source-id: e92c9822d9226681d7b00126dad95e5534c0c46e

ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactTextInputManager.java

@@ -49,6 +49,7 @@
 import com.facebook.react.uimanager.events.EventDispatcher;
 import com.facebook.react.views.imagehelper.ResourceDrawableIdHelper;
 import com.facebook.react.views.text.DefaultStyleValuesUtil;
+import com.facebook.react.views.text.ReactFontManager;
 import com.facebook.react.views.text.ReactTextUpdate;
 import com.facebook.react.views.text.ReactTextView;
 import com.facebook.react.views.text.TextInlineImageSpan;
@@ -190,7 +191,10 @@ public void setFontFamily(ReactEditText view, String fontFamily) {
     if (view.getTypeface() != null) {
       style = view.getTypeface().getStyle();
     }
-    Typeface newTypeface = Typeface.create(fontFamily, style);
+    Typeface newTypeface = ReactFontManager.getInstance().getTypeface(
+        fontFamily,
+        style,
+        view.getContext().getAssets());
     view.setTypeface(newTypeface);
   }