fix: first time running shorebird release took a long time before showing "fetching apps"

[nateshmbhat]

App ID: 007a2cb9-86ee-4f73-90db-1d3322af1863

Description
I ran shorebird release on a starter flutter app and i was confused why nothing is happening, i cancelled and re-ran the command again few times, every time no response. then i waited for like 10 minutes and then it proceeded normally as expected and the rest of the console messages showed up.

This only happened for 1st time release happened, then after that i'm not able to repro this issue

Steps To Reproduce
i don't know how to repro this.

Expected Behavior

shorebird release doesn't get stuck for such long times

[bryanoltman]

I believe this is because we're downloading bundletool in the background. We should probably show a progress spinner or similar.