[FEATURE] Use Cronet network backend

[markg85]

Describe the bug Currently no backend is explicitly used which apparently makes it use okhttp.

To Reproduce Steps to reproduce the behavior (required the ability to set breakpoints!):

1. Run NextPlayer in debug
2. Set a breakpoint in DefaultHttpDataSource.java on the read(...) function
3. Play a http(s) video
4. Inspect the breakpoint carefully, ou'll see okhttp mentions there.

Expected behavior ExoPlayer has a couple network backends, they recommend using Cronet. I guess it makes sense to follow the recommendation.

Screenshots N/A

Device info (please complete the following information): Irrelevant

Additional context So, in my specific case i'm trying to profile why playing a large - say 20GB representing 150 video minutes - file is having troubles playing on a chromecast. 20GB (say 20000MB) / 9000 (150 minutes = 9000 seconds) = ~2.2MB/s for smooth playback. I'm doing my experiments in the Cronet backend as that's recommended. Hence I find it quite convenient if this project switches to Cronet too. Just selfish reasons ^_^