ci: Refactor workflows to be snap centric

[tim-hm]

Currently workflows/ci.yml is doing a lot of jobs across a lot of apps. For example it is testing and and building bootstrap which includes working with a subiquity submodule, taking screenshots in a VM etc. Then, there is init which is a flutter snap frontend and a golang backend shipped as a deb.

I think we could improve the pipeline to be app focused. For example, a bootstrap-ci.yaml and an init-ci.yaml where each is tailored to the artefacts it produces and languages and package formats bespoke to each. Some exploration is required here, but I think this subiquity_integration comment, #443 (review), highlights the current structure isn't quiet right.

Straw man structure to illustrate:

.github/workflows
  - bootstrap-ci-cd.yaml
  - init-ci-cd.yaml
  - sync-gh-to-jira.yaml
  - cla-check.yaml