Add prop to configure importantForAutofill. (#22763)

Summary:
In API 26, autofill framework was introduced in Android.
Read more about Autofill at https://developer.android.com/guide/topics/text/autofill.

Now, if in case for some text input if developer wants to disable
autofill then he can take help from this `importantForAutoFill` prop
and pass `no` to it.

Also important of auto fill can be configured with this prop, like:
* `auto`: Let the Android System use its heuristics to determine if the view is important for autofill.
* `no`: This view isn't important for autofill.
* `noExcludeDescendants`: This view and its children aren't important for autofill.
* `yes`: This view is important for autofill.
* `yesExcludeDescendants`: This view is important for autofill, but its children aren't important for autofill.

Default value if `auto`.

Read more at: https://developer.android.com/guide/topics/text/autofill-optimize

Changelog:
----------
[Android] [Added] - Add prop to configure `importantForAutofill` in `TextInput`.
Pull Request resolved: https://github.com/facebook/react-native/pull/22763

Differential Revision: D14121242

Pulled By: cpojer

fbshipit-source-id: aa4360480dd19f6dde66f0409d26a41a6a318c94

Libraries/Components/TextInput/TextInput.js

@@ -245,6 +245,13 @@ type AndroidProps = $ReadOnly<{|
   underlineColorAndroid?: ?ColorValue,
   inlineImageLeft?: ?string,
   inlineImagePadding?: ?number,
+  importantForAutofill?: ?(
+    | 'auto'
+    | 'no'
+    | 'noExcludeDescendants'
+    | 'yes'
+    | 'yesExcludeDescendants'
+  ),
 |}>;
 
 type Props = $ReadOnly<{|