underlineColor transparent not working on API 21 (#30897)

Summary:
This issue fixes https://github.com/facebook/react-native/issues/29379 `underlineColorAndroid'='transparent'` does not work on Android API 21.
Setting `style: { bottomBorderColor: 'transparent'}` fixes the issue.

The following steps fix underlineColorAndroid on Android API 21:
- Store the bottomBorderColor in a local variable
- Then set the bottomBorderColor to the same color of underlineColorAndroid
- Set underlineColorAndroid
- Then Set the bottomBorderColor to the previous color previously stored in the local variable

This change requires `ReactViewBackgroundDrawable` method `getBorderColor` to be public and accessible from `ReactTextInputManager` to retrieve the border color.

https://github.com/facebook/react-native/blob/6061b7928320c64a94716ce3d6646667ebf3f6b5/ReactAndroid/src/main/java/com/facebook/react/views/view/ReactViewBackgroundDrawable.java#L1231-L1236

Related Discussions https://github.com/facebook/react-native/issues/18938 https://github.com/facebook/react-native/pull/18988 https://github.com/facebook/react-native/issues/29412#issuecomment-773412466

More Information at https://github.com/fabriziobertoglio1987/react-native-notes/issues/4#issuecomment-1029780852

## Changelog

[Android] [Fixed] - Fix underlineColorAndroid transparent not working on API 21

Pull Request resolved: https://github.com/facebook/react-native/pull/30897

Test Plan:
This changes fix the Java API which can not be tested as explained in commit https://github.com/facebook/react-native/commit/709a441ecf54cd9465f5946af0454ee7d10d5cbe
The java TextInputTest was excluded from the test suite in commit https://github.com/facebook/react-native/commit/709a441ecf54cd9465f5946af0454ee7d10d5cbe as they need the Yoga libraries to run

**<details><summary>CLICK TO OPEN TESTS RESULTS - API 21</summary>**
<p>

Does not show underline by default (`transparent`)

```javascript
<TextInput />
```

<image src="https://user-images.githubusercontent.com/24992535/107060953-dee34d00-67d7-11eb-8f01-360dbb1420b8.png" width="150" />

```javascript
<TextInput underlineColorAndroid="red" />
```

<image src="https://user-images.githubusercontent.com/24992535/107061134-194cea00-67d8-11eb-9da1-9780b1aa8294.png" width="150" />

```javascript
<TextInput
  underlineColorAndroid="green"
  style={
     {
        borderBottomColor: 'red',
        borderBottomWidth: 2,
        borderTopColor: 'black',
        borderTopWidth: 4
     }
   }
/>
```

<image src="https://user-images.githubusercontent.com/24992535/107062411-9167df80-67d9-11eb-810c-749992d8d2d3.png" width="150" />

```javascript
<TextInput
  style={
     {
        borderBottomColor: 'red',
        borderBottomWidth: 2,
        borderTopColor: 'black',
        borderTopWidth: 4
     }
   }
/>
```

<image src="https://user-images.githubusercontent.com/24992535/107062735-e6a3f100-67d9-11eb-93c3-02cd768f8421.png" width="150" />

```javascript
<TextInput
  underlineColorAndroid="blue"
  style={
    {
      borderBottomColor: 'red',
      borderBottomWidth: 2,
      borderTopColor: 'black',
      borderTopWidth: 4,
      borderLeftColor: 'pink',
      borderLeftWidth: 7,
      borderRightColor: 'yellow',
      borderRightWidth: 7,
    }
  }
/>
```

<image src="https://user-images.githubusercontent.com/24992535/107063263-75b10900-67da-11eb-97ab-316736d525a2.png" width="150" />

```javascript
<TextInput
  underlineColorAndroid="transparent"
  style={
    {
      borderBottomColor: 'red',
      borderBottomWidth: 2,
      borderTopColor: 'black',
      borderTopWidth: 4,
      borderLeftColor: 'pink',
      borderLeftWidth: 7,
      borderRightColor: 'yellow',
      borderRightWidth: 7,
    }
  }
/>
```

<image src="https://user-images.githubusercontent.com/24992535/107063332-8792ac00-67da-11eb-82fc-99793bf4d49d.png" width="150" />

</p>
</details>

Reviewed By: cortinico

Differential Revision: D33906415

Pulled By: lunaleaps

fbshipit-source-id: bd7efe4aac40ad701aec83f051ac40dcd4a99cda