Fix auto-CLI documentation generation

[frouioui]

A while ago we started a project with the goal of automating the generation of our CLI documentation. After a while we observed that the Pull Requests created by the bot to update the CLI documentation were not 100% correct and eventually they stopped being correct. This issue tracks the items left to complete this feature:

• The Preview PR is very noisy, lot of code change when we only care about maybe one flag.
• The Preview PR should be created as a draft with a proper description to explain what its purpose is.
• The Preview PR's title can be simplified if we mark the PR as a draft from the beginning.
• When we close the Vitess PR, the Preview PR is not transformed into a normal PR. This step is not working correctly right now.
• In some cases when synchronizing or opening a new Vitess PR with a flag change, the tooling inside the website repository will not detect any change and thus fail the whole bot's workflow.
• The state of the git repo is not cleaned correctly, leading in some very precise case to git checkout failing because of stale files in the clonned repository.
• We do not currently lock our two temporary repository when performing actions on them like checkout, reset, etc. Which can lead, in some cases (when modifying/opening/closing multiple PRs on vitess at once), to big concurrency issues that are not handled. This applies to both error code generation and documentation generation, but is worse with documentation generation as some of the action we perform take quite some time, exposing the code to more higher risk of data race.
• The release handler is not working at all as of right now.