Expose adjustsFontSizeToFit as new prop for Button

**Is your feature request related to a problem? Please describe.**
On some devices button text gets truncated due to `numberOfLines={1}` being applied to the `Text` label.

**Describe the solution you'd like**
`adjustsFontSizeToFit` exists and provides an easy way to keep the entire label visible.

**Describe alternatives you've considered**
I have attempted to do this myself by passing a `Text` element as a child to the button like so:
```

{text}

```
This unfortunately did not work. Only by editing the `Button` itself did iOS respect the `adjustsFontSizeToFit` prop.
**Additional context**
It looks like there is an existing pull request for this (although it's missing context):
#4125

从渲染 Text 标签的 Button 实现入手，然后查看 pull request #4125 的上下文。将 adjustsFontSizeToFit 暴露为 Button prop，并验证当文本原本会被截断时，标签在 iOS 上仍保持可见。

由索引模型根据 Issue 内容生成。