Restructured inheritance around ReactTextViewManager and co.

Summary:
Abstract class `ReactBaseTextShadowNode` was decoupled from `ReactTextShadowNode` to separate two goals/roles:
 * `ReactBaseTextShadowNode` represents spanned `<Text>` nodes, which can bear text attributes (both `RCTText` and `RCTVirtualText`);
 * `ReactTextShadowNode` represents anchor `<Text>` view in Yoga terms, which can bear layout attributes (`RCTText` and `RCTTextInput`).

`ReactVirtualTextShadowNode` now inherits `ReactBaseTextShadowNode`.
The same architectural changes was applited to view managers.

Why?
 * This is just a better architecture which represents the nature of this objects.
 * Bunch of "negative" logic which turn off excessive features for some suclasses was removed.
 * Memory efficiency.
 * Now we can improve `<TextInput>` component using right inheritance. Yay!

Reviewed By: achen1

Differential Revision: D5715830

fbshipit-source-id: ecc0764a03b5b7586fe77ad31f149cd840f4da41

Author: shergin

ReactAndroid/src/main/java/com/facebook/react/flat/RCTTextInput.java

@@ -9,19 +9,15 @@
 
 package com.facebook.react.flat;
 
-import javax.annotation.Nullable;
+import static com.facebook.react.views.text.ReactRawTextShadowNode.PROP_TEXT;
+import static com.facebook.react.views.text.ReactTextShadowNode.UNSET;
 
 import android.annotation.TargetApi;
 import android.os.Build;
 import android.text.SpannableStringBuilder;
 import android.util.TypedValue;
 import android.view.ViewGroup;
 import android.widget.EditText;
-
-import com.facebook.yoga.YogaMeasureMode;
-import com.facebook.yoga.YogaMeasureFunction;
-import com.facebook.yoga.YogaNode;
-import com.facebook.yoga.YogaMeasureOutput;
 import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.Spacing;
@@ -32,9 +28,11 @@
 import com.facebook.react.uimanager.annotations.ReactProp;
 import com.facebook.react.views.text.ReactTextUpdate;
 import com.facebook.react.views.view.MeasureUtil;
-
-import static com.facebook.react.views.text.ReactTextShadowNode.PROP_TEXT;
-import static com.facebook.react.views.text.ReactTextShadowNode.UNSET;
+import com.facebook.yoga.YogaMeasureFunction;
+import com.facebook.yoga.YogaMeasureMode;
+import com.facebook.yoga.YogaMeasureOutput;
+import com.facebook.yoga.YogaNode;
+import javax.annotation.Nullable;
 
 public class RCTTextInput extends RCTVirtualText implements AndroidView, YogaMeasureFunction {