* Alerting: Cleanup and move legacy to a legacy file
A quick cleanup of the ngalert/api directory, optimising for an easy
removal of what is will be considered legacy at some point. A quick
summary of what's done is:
- Add a prefix `generated` prefix to files that are auto-generated by
our swagger definitions.
- Create a legacy file to place all the legacy API routes implementation
and helpers. Deleting files that where no longer needed after this
move.
- Rename the `lotex` file to `lotex_ruler`
- Adding a couple of comments here and there.
With this, I hope to organise our code in this directory a bit better
given there's a lot going on.
