autosave: put files into git

As a developer i think it would be useful to have the autosave directory in git to version it? Blockserver could push periodically like for configs, we could move autosave from var to settings and create a junction for backward compatibility. If we moved it into the config area i think it could get git versioned for free by blockserver as opposed to a separate settings git.

## Acceptance criteria

* plan for moving autosave to git, may involve upgrade action or just apply to all instruments
* appropriate gitignore so onl current version e.g. `*.sav` put into git and not all the date formatted ones that are created each ioc start

## Planning
planning 01:05 2025/03/06