[eas-cli] Automatically migrate build credentials to EAS

[brentvatne]

Hotfix for issue resulting in developers ending up in half-migrated credentials state

[github-actions]

Size Change: +819 B (0%)

Total Size: 37.6 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	37.6 MB	+819 B (0%)

_{compressed-size-action}

[quinlanj]

I'm debating whether it'd be a better user experience all around if we just scrapped all uses of promptForNameAsync and replaced it with generateRandomName() :/