[Compose] Expose Glide loading status as an observable state.

[mhozza]

Issue details / Repro steps / Use case background:

We would like to show / hide some other UI based on the glide loading status. It would be great if Glide could expose observable loading state that could be used for this:

API Example:

val glideState = rememberGlideState()

GlideImage(glideState, ...)

if(glideState.status == Status.SUCCEEDED) {
  ShareButton(...)
}