Unresolved reference: `mainFileCache`

### Description

Updated Fresco version from 2.6.0 to 3.4.0.
Function `ImagePipelineFactory.getMainFileCache()` does not exist anymore in 3.4.0.

### Reproduction

```
val imageRequest = ImageRequest.fromUri(url)

val cacheKey = DefaultCacheKeyFactory
.getInstance()
.getEncodedCacheKey(imageRequest, null)

val resource = ImagePipelineFactory
.getInstance()
.mainFileCache // Unresolved reference: mainFileCache
.getResource(cacheKey)

val file = (resource as? FileBinaryResource?)?.file
```

### Solution

How do I change the above code to work in 3.4.0?
It would be helpful if the function was marked as deprecated before completely removing it.

### Additional Information

* Fresco version: 3.4.0
* Platform version: 33