refactor github actions

[NdibeRaymond]

as @yokwejuste pointed out in the recent auto-create-test-vm action PR, our github actions are a bit outdated and requires some refactoring. Though they still work, it makes sense to update them. Things that needs to be done in no particular order:

• [x] use matrix strategy for similar jobs to save time
• [x] update version of third-party actions
• [x] use composite actions
• [ ] improve readability
• [x] add action to auto perform docker system prune on all desired vm before or after each deployment.
• [x] remove QEMU from github actions (since we are not doing multi-platform build)

[yokwejuste]

Also, I was thinking of us having some few variables there and making the code more human-readable. We can be dropping the suggestions here.