Auto select first device when there is no selection yet

[Lootwig]

This change automates the requirement to manually select a device, currently a mandatory manual step when not running from the command line (flutter run is capable of autonomously selecting a matching device)

Fixes #7970.

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read the [Flutter Style Guide] recently, and have followed its advice.
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.

[AlexV525]

(Personal suggestion) Since there is no test in the PR, could you attach a screen recording of how it runs?