[services] Backup - reset implementation

Summary:
The new API of the backup service will be significantly different from the current one, so I decided to simply remove everything. It's still going to be in the git history so we can get back to it any time but removing it will make testing and implementation process easier.

Test Plan: -

Reviewers: geekbrother, palys-swm, varun, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: benschac, ashoat, palys-swm, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D3077