Request: offer a flag to avoid auto-recycling of a Bitmap instance

```
implementation("com.github.bumptech.glide:glide:5.0.0-rc01")
ksp("com.github.bumptech.glide:ksp:5.0.0-rc01")
```

I use this simple call to get some Bitmap that I want to use right away in the current thread (and maybe even use it somewhere else), and as I don't want the cache to work here (I replace the same file with a different file later), I also disable it:

```
val bitmap =Glide.with(applicationContext).asBitmap()
.load(file)
.apply(RequestOptions.centerCropTransform().skipMemoryCache(true).diskCacheStrategy(DiskCacheStrategy.NONE))
.submit(photoThumbnailSize, photoThumbnailSize).get()
//use the bitmap right here (not into ImageView)
```

I've noticed that I got some crashes reported here via Crashlytics, saying the bitmap is recycled, so I can't use it...
The reason is that there is no reference anymore to the FutureTask, so Glide is auto-recycling the Bitmap:

https://bumptech.github.io/glide/doc/resourcereuse.html#reference-counting

I might be able to overcome this by copying the result bitmap while also having a reference to the task:

```
val futureTarget: FutureTarget = Glide.with(applicationContext)
.asBitmap()
.load(file)
.apply(RequestOptions.centerCropTransform().skipMemoryCache(true).diskCacheStrategy(DiskCacheStrategy.NONE))
.submit(photoThumbnailSize, photoThumbnailSize)
val bitmap: Bitmap? = futureTarget.get()
//copy the bitmap to a new instance here, instead of using it wherever I wish...
```

But this is a bad workaround as it uses double the memory, and even here I'm not sure it will work. Maybe it will cause GC before I copy the Bitmap as there is no use of the "futureTarget" anymore (optimization by the GC), and recycle the Bitmap?

Anyway, please offer a way to overcome this, to let me do the decoding&downsampling operation without the danger of my bitmap being recycled by Glide.