[instant] Handle more instant declaration patterns (#90251)
Adds handling for
```tsx
export { unstable_instant } from './config'
^
```
```tsx
const unstable_instant = ...
^
export { unstable_instant }
```
```tsx
const instant = ...
^
export { instant as unstable_instant }
```
We're not following assignments recursively and stop at the first declaration:
```tsx
const _instant = ...
const instant = _instant
^
export { instant as unstable_instant }
```
