Add optional detached deployment option

[som-matrix]

• This PR introduces the ability to control the deployment behavior of the Fly app within our GitHub Actions workflow. Users can now specify whether the deployment should run in a detached mode, which allows the GitHub Actions runner to proceed without waiting for the deployment to complete. This feature is particularly useful for workflows where immediate feedback from the deployment process is not necessary, helping to reduce wait times and potential bottlenecks in continuous integration pipelines.

Changes

• Added a new environment variable INPUT_WAIT, which users can set to true if they wish for the deployment to wait until completion. By default, the deployment runs in detached mode.
• Modified the flyctl deploy command to accept a --detach flag based on the INPUT_WAIT setting, enabling either immediate return or waiting for the deployment process.