Add code to revert back repo renames

[decyjphr]

When a repo is renamed outside safe-settings we want to revert it back to the original name.

We get the repository.renamed event and the payload has the previous name in it.

Then, we can simply call Settings.sync with the repo settings for the old name. This will revert the changes because when we call the api to get a repo with the old name it will retrieve the repo with the new name automatically. And the rest is easy as if we are applying the settings to the repo normally with repo name as the old name.

[decyjphr]

Adding this functionality does add complications.

1. First, if safe-settings prevents renaming of repos by humans, then it should allow for a way to rename repos using safe-settings itself. For this, the logical thing to do is to allow users to request a repo rename by renaming the repo/<repo>.xml. This is implementable because, when a push happens we can detect rename of <repo>.xml and do the rename operation. Similarly, in the PR workflow, we can detect a rename and report that as a change.
2. We don't want to block existing users of safe-settings by suddenly reverting repo renames in their orgs. So I am thinking of enabling this feature only when it is explicitly enabled in the <deployment-config> like using a setting block_repo_rename=true

I am interested in your thoughts. Please let me know.

[decyjphr]

Added code so that:

If a repository is renamed, the default behavior is safe-settings will ignore this (for backward-compatibility).

If BLOCK_REPO_RENAME_BY_HUMAN env variable is set to true, safe-settings will revert the repo to the previous name unless it is renamed using a bot.

If it is renamed using a bot, it will try to copy the existing <old-repo>.yml to <new-repo>.yml so that the repo config yml stays consistent. If the <new-repo.yml> file is already existing, it doesn't create a new one.

If you rename a <repo.yml> that corresponds to a repo, safe-settings will rename the repo to the new name. This behavior will take effect whether the env variable BLOCK_REPO_RENAME_BY_HUMAN is set or not.