GitHub Workflows security hardening

[sashashura]

This PR adds explicit permissions section to workflows. This is a security best practice because by default workflows run with extended set of permissions (except from on: pull_request from external forks). By specifying any permission explicitly all others are set to none. By using the principle of least privilege the damage a compromised workflow can do (because of an injection or compromised third party tool or action) is restricted.
It is recommended to have most strict permissions on the top level and grant write permissions on job level case by case.

[OskarStark]

Should be merged against 4.4

[sashashura]

Do you mean also or instead?

[OskarStark]

Instead please, we will then upmerge your change to newer branches

[wouterj]

Please note that we can switch branches during the merge, so there is nothing for you to do (if you don't know how to do it or don't have the time to do it).

[sashashura]

Please note that we can switch branches during the merge, so there is nothing for you to do (if you don't know how to do it or don't have the time to do it).

Please do. I just made a pull request against the default branch.

[OskarStark]

Thank you @sashashura.