Workaroud yes not allowed for edge promotions (infra)

[Hook25]

Description

Snapcraft doesn't natively allow to non-interactively promote a snap from an un-branched edge channel as it can be seen here(link). We need this feature as we do use an unbranched edge channel and we want to automatically promote to beta the builds. This PR removes the --yes switch replacing with yes |.

Note: This would not work as snapcraft will try to understand if it is in an interactive session or not. To make snapcraft just use the input provided in stdin, the SNAPCRAFT_HAS_TTY envvar is also added.

Resolved issues

Failing build: https://github.com/canonical/checkbox/actions/runs/7112360707/job/19362163613

Documentation

A comment documents why we need the environment variable and the yes | workaround

Tests

I will launch the workflow from this branch before merging

[kissiel]

Tried myself with my testing snap and got to the same dead end, indeed this looks like the only way out of this mess.