Update workflow configs

[Kichura]

1. Adds a cooldown system for Dependabot to freeze version updates, (exception being security updates)
2. Changes the CI's contents permission to read-only - However use write if a specific repository absolutely requires it,
3. Pins all job versions to their commit hashes to avoid supply chain attacks towards the workflow script,
4. Moves all environment mentions into the env: section to prevent causing them from getting expanded into attacker-controllable code,
5. Adds the timeout-minutes to the job(s) section so that the CI doesn't take 6 hours straight to get aborted in case something is causing the CI to suddenly stall or become unresponsive, (this can be adjusted if 30 mins is too short or too long)
6. Renames the main workflow -> check aswell as build -> test to be consistent with actual CI titles.

(All security issues were spotted by the zizmor library)

[kennytv]

Thanks!