Fixed TextInput not being selectable in removeClippedSubviews FlatLis…

…ts (#28852)

Summary:
This is a resubmit of D21499015. It resolves #28852 and #27787.

From Harry Yu's original PR (too old to merge now):

Text in TextInputs can't be selected by long press. This happens only when they're inside of FlatLists that are rendered with removeClippedSubview prop set to true on Android.

Fixes #27787

Issue #6085 2 years ago had fixed this issue with a quick fix, but the code has since disappeared in another change. It has a longer explanation for why it's fixed, but essentially - the text is assumed to be not selectable since the TextInput is initialized without being attached to the window. We need to explicitly set the text to be selectable on attachment. This change redoes that change with a 1-line fix.

Changelog: [Android] [Fixed] - Fixed TextInput not being selectable in removeClippedSubviews FlatLists

Pull Request resolved: #28852

Test Plan:
This can be tested with a new toggle in RNTesterApp.
Go to the FlatList in RNTesterApp
Toggle on "removeClippedSubviews"
Try selecting some text in the list header. It should fail without this comment but succeed with it

Reviewed By: sammy-SC

Differential Revision: D24043533

Pulled By: JoshuaGross

fbshipit-source-id: c8e60f8131ccc5f6af31ed976c4184d0a16eb3af

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

@@ -827,6 +827,13 @@ public void onStartTemporaryDetach() {
   @Override
   public void onAttachedToWindow() {
     super.onAttachedToWindow();
+
+    // Used to ensure that text is selectable inside of removeClippedSubviews
+    // See https://github.com/facebook/react-native/issues/6805 for original
+    // fix that was ported to here.
+
+    super.setTextIsSelectable(true);
+
     if (mContainsImages) {
       Spanned text = getText();
       TextInlineImageSpan[] spans = text.getSpans(0, text.length(), TextInlineImageSpan.class);