[BUG]: The get-architectures job does not support projects that don't specify the architectures and platforms property

[brlin-tw]

What changes would you like?

Currently, the get-architectures workflow will return an empty array on projects that have snapcraft.yaml not declaring any platforms and architectures, making the release-to-candidate workflow error with the following message:

Error when evaluating 'strategy' for job 'release'. .github/workflows/release-to-edge.yaml (Line: 36, Col: 23): Matrix vector 'architecture' does not contain any values

It should rather return the full list of architectures that Launchpad supports building on that base, which matches the behavior of snapcraft.io/build

Any extra information?

No response