Draft: Prepare files for change of main branch name

[dudoslav]

This PR changes all mentions of the dev branch as the default branch to branch name main. This whole change will require us to atomically:

1. Merge this PR
2. Create a new branch main from dev and make sure not to merge any PR's until this whole process is done
3. Change the default branch of this project to main
4. Change all mentions of dev branch in our repositories to be changed to main (This can be done retroactively)

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TYPE: NO_HISTORY
DESC: Change all mentions of default branch

[teo-tsirpanis]

Some unrelated instances of dev were renamed to main.