Android: Offload cover path unmangling to another thread

[t895]

As mentioned by @JosJuice in #11245, I have offloaded the unmangling of the custom cover path to another thread.

(On UI Thread)
Performance Before -

Performance After -

[JosJuice]

Is there a reason why the Glide call has to happen on the main thread? I'm particularly thinking about the fact that File.exists is being called on the main thread. (It's faster than unmangle, but it still has to hit the file system.) Though I suppose if the Glide call does have to happen on the main thread, you could move just the File.exists call to the unmangle thread.

[t895]

Is there a reason why the Glide call has to happen on the main thread? I'm particularly thinking about the fact that File.exists is being called on the main thread. (It's faster than unmangle, but it still has to hit the file system.) Though I suppose if the Glide call does have to happen on the main thread, you could move just the File.exists call to the unmangle thread.

Yeah Glide has to be called on the main thread because it posts the result to the imageView. But I'll just move the File.exists call to make things a little better.