[Feature Request] Start downloading next item in queue after last one begins extracting

[flanter21]

Is your feature request related to a problem? Please describe.

• When updating things from Universal Updater, sometimes it takes a long time to extract. (I'm looking at you NZ Portable). Combined with the slow 3DS wifi speed, it can take a long time for everything to finish.
• If instead, Universal Updater could download the next item while the current item was installing/extracting, things would be faster.

Describe the solution you'd like:

1. First program downloads.
2. First program extracts and second program downloads concurrently.

Current behaviour:

1. First program downloads.
2. First program extracts.
3. Second program downloads.

Describe alternatives you've considered: N/A

Additional context: N/A