Support incremental build in CI/CD

[freddydk]

Feedback from Directions EMEA 2024

When working with repositories containing multiple apps, it is very time consuming to build and deploy new versions of all apps even though they haven't been changed.

We should support only rebuilding modified apps and their dependencies and then grab all unchanged apps from the last successful build. At the same time, when calculating which apps should be build - we should use the SHA from the last successful build as foundation for determining which apps have modifications and needs rebuilding.

This also means that we can add concurrency to CI/CD, as every build will build everything necessary since last successful.