TextInput: Only highlight bottom line when focused

[krizpoon]

Motivation

The TextInput should only be highlighted when focused or in error state. #436

Test plan

1. Focus the text input. The label color and the bottom line color should be the primary theme color and the bottom line highlighted.
2. Blur the text input. The color should be the disabled color and the bottom line is not highlighted.
3. Enter some text and blur the text input. The color should be the disabled color and the bottom line is not highlighted.
4. Set text input in error state, the color should be the error color and the bottom line is highlighted.

[callstack-bot]

Hey @krizpoon, thank you for your pull request 🤗. The documentation from this branch can be viewed here.

[satya164]

merged in a19ffa0