Override reactAccessibilityElement for RCTTextView

[FalseLobster]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary:

RCTTextView does not override reactAccessibilityElement to the RCTUnfocusableTextView child. This causes various properties, like accessible, to not get applied correctly.

In VoiceOver, there's a bug where if you have a Touchable like so:

<TouchableOpacity
        accessibilityRole="button"
        accessibilityLabel="Button with accessibility role as button and label"
        onPress={onPress}>
        <Text>Button with A11y Label Defined</Text>
</TouchableOpacity>

It reads "button, group". By making the accessible prop apply correctly, the user can set the <Text accessible={false} /> and VoiceOver will just read "button".

Before:

After:

Changelog:

[INTERNAL] [FIXED] - Make accessibility props apply correctly to components on macOS.

Test Plan:

See Summary