FR (Authenticator): Support dynamic text update when changing languages

**Is your feature request related to a problem? Please describe.**
Components are not re-rendering on `I18n.setLanguage`. Components are rendering initial language strings correctly but they do not re-render on language change.

_Relates to aws-amplify/amplify-js#6346 aws-amplify/amplify-js#6115 #6962_

**Describe the solution you'd like**
Components should re-render on `I18n.setLanguage`

_Suggestion from @ericclemmons https://github.com/aws-amplify/amplify-js/pull/6346#issuecomment-710227501 :_
> If I18n.setLanguage fired a Hub event, we _could_ re-render the component 🤔
> https://github.com/aws-amplify/amplify-js/blob/377acd0507e6d4be34bf36ea9c0694fa98ac04b1/packages/core/src/I18n/I18n.ts#L64-L66

**Describe alternatives you've considered**
1. Force re-render using `key` attribute
```jsx

```
Force re-creating the components will result in a screen flicker and loss of component state
2. Specifying all texts in props
```jsx


```
Doable but a big hassle : D

**Additional context**
This is happening in `@aws-amplify/ui-react`.
Need to check if other ui-components e.g. angular, vue, etc exhibit the same behavior.

Start with packages/core/src/I18n/I18n.ts, especially the setLanguage path referenced in the issue, and inspect how @aws-amplify/ui-react components obtain translated text. Check whether other UI components such as Angular or Vue have the same behavior. Done means components re-render after I18n.setLanguage without a key workaround, screen flicker, or loss of component state.

Written by the indexing model from the issue text.