Implement back-compat tests to ensure new Bicep versions can consume modules published by previous versions - and previous versions of bicep can consume modules published by newer ones

This will ensure that there are no surprises when users upgrade Bicep to a new version that prevent previously published modules from being consumed.

One idea is to have release/official builds publish some sample artifacts to a persistent ACR and another test consume artifacts published by previous releases.

Start with the release/official builds and the proposed persistent Azure Container Registry (ACR). Define how sample artifacts from each release are published and how tests consume artifacts from both previous and newer Bicep versions. Done means upgrades and downgrades can verify module compatibility without surprises.

Written by the indexing model from the issue text.